I am not going to spend hours at this site being distracted by bored morons who want me to prove things that are self-evident (this is not a reference to you at all, just a general comment). With respect to the question of Marcion's repentance, I happen not to believe the report for several reasons and I - as an aside - suspect the reason you believe it is because you have fallen victim to the silly notion that Marcion was anti-Semitic and so believe the Church Fathers when they right buttons for you.
Let me address the issue as best I can here. There is a relationship between parts of the Prescription and Adversus Haereses Book 3. This is undeniable. Whether or not Irenaeus wrote both texts and Tertullian - as he did with Adv Iud and Adv Marc 3 - blended and rearranged bits of Irenaeus's original treatises with his own thoughts - or as others might argue, he wrote the Prescription being influenced by thoughts or things he read from Irenaeus, the underlying point is the same. The relationship between the Prescription and Adv Haer 3 is key.
In the Prescription the report that Marcion became a Christian (i.e. an orthodox for Tertulian elsewhere says that anyone who is Christian has to be orthodox and vice versa) and repented or whatever comes in the section THAT IS MOST RELATED to Adv Haer 3. I will highlight again the clear signs that connect the passage to the Adv Haer 3 and especially the argument that develops from a canonical succession list at Rome:
or it is agreed that they lived not so very long ago in the reign of Antoninus (138 - 161) for the most part, and that at first they were believers in the doctrine of the Catholic Church in Rome during the episcopate of the blessed Eleutherus, until, on account of their ever restless speculation whereby they corrupted the brethren also, they were expelled more than once—Marcion, indeed, with the two hundred sesterces that he had brought into the Church—and when at last banished into perpetual separation from the faithful, they spread abroad the poisonous seeds of their peculiar doctrines. Afterwards, when Marcion had professed penitence and agreed to the condition imposed upon him, namely, that if he could bring back to the Church the residue whom he had instructed to their perdition, he should be received into communion, he was prevented by death.
It is my contention that this comment should be properly contextualized as a continuation of what is said in Adv Haer 3 where with the coming of Polycarp "in the time of Anicetus caused many to turn away from the aforesaid heretics (Marcion, Valentinus) to the Church of God."
So if we set up a time line Tertullian is saying in effect (because he certainly knew of the Anicetus story).
Once upon a time Marcion was at Rome and was influential. He was originally referenced as Marcellina in Irenaeus's source Hegesippus (but apparently that shouldn't concern us that 'Marcellina' changes sex and name and becomes 'Marcion' under Irenaeus's hand). In any event after a sex change operation and a name change Tertullian pick up our story. Marcion is now trying his best to adapt to life under the new regime established by Polycarp. He on the surface wants to be a faithful Catholic. That's what the "at first they were believers in the doctrine of the Catholic Church in Rome " is all about. We are in the age of Eleutherus now but the "ever restless speculation whereby they corrupted the brethren also, they were expelled more than once" reference tells you that we are now in the territory of the story cited in Adv Marc 3:
And Polycarp himself replied to Marcion, who met him on one occasion, and said, "Dost thou know me?" "I do know thee, the first-born of Satan." Such was the horror which the apostles and their disciples had against holding even verbal communication with any corrupters of the truth; as Paul also says, "A man that is an heretic, after the first and second admonition, reject; knowing that he that is such is subverted, and sinneth, being condemned of himself."
Clearly the same idea is present here. Polycarp who came to Rome under Anicetus to introduce us to Marcion established orthodoxy there and Marcion tried to adapt himself to the new rules. However by the time he asked to recognized, Marcion had already reached the two strikes and your out rule from the Pastoral epistles. That's why we should see the 'asking Polycarp to be recognized' and the purchasing of the church as one and the same historical 'moment.' For when the Prescription says:
they were expelled more than once—Marcion, indeed, with the two hundred sesterces that he had brought into the Church—and when at last banished into perpetual separation from the faithful
The giving of two hundred sesterces is the lead up to asking Polycarp to be recognized both of which end with him being permanently banned from the Church.
The general idea here is that Marcion was given two chances as the Pastoral decree sets forth. This is clearly set up to make it seem as if the Pastoral decree was already established and part of the operation of churches in the middle of the second century which is a lie. The Pastoral Epistles were likely only written at that time and were certainly not part of the operating 'rules' of a worldwide Church at this time so that's Strike One for us.
So if the part about Marcion being ejected because of two strikes is made up let's move on to look at the two strikes. Epiphanius says he had been under excommunication went he went to Rome. Apparently he had doctrinal issues and a rape of a girl in his father's see. But there are obvious inconsistencies with Epiphanius's story too. The idea is here that the Roman Church can't reverse the decision of a provincial see which certainly wasn't true in 150 CE. There was no worldwide Church network nor any complex rules of this sort. Furthermore Epiphanius adds the incongruous addition that Marcion was upset that he didn't get restored as bishop (so which was it, excommunication or being a bishop).
The facts are that Marcion was a bishop. This is lurking in the background of all the reports. So too is the idea that Marcion died at an old age. So I don't know which period you think Marcion died. The placement of this deathbed repentance is now the age of Eleutherus so 170 CE is already hard to accept. Clement says he was an old man in the age of Hadrian. But dismissing Clement and Marutha Irenaeus says that Polycarp visits during Anicetus, Tertullian claims he accepted Catholicism, then he was finally ejected from the Church (the first strike being apparently at the time of his conversion by Polycarp i.e. when he must have promised to stop believing and practicing things counter to Catholic doctrine).
The bottom line for me is that there is just so much contradictory evidence about Marcion. Scholars want to line these all up so we have a 'real person' and something to write about. But there is almost no commonality between Clement and Marutha's 'apostolic Marcion' who likely lived from the time of Jesus to Hadrian and Irenaeus and Tertullian's 'Antonine Marcion' who was spoken about by Justin during the reign of Antoninus Pius (138 - 161) and who lived until Eleutherus (170 - 180 CE) and Epiphanius's 'rapist Marcion.'
The historical accounts of Marcion don't agree because there likely wasn't a historical Marcion. Marcion began life with a sex change and a name change (as noted) and then was essentially invented by Irenaeus and written into Justin Martyr's Apology by Irenaeus
in order to prove that Marcellina was a mistake of the edition of Hegesippus's Chronicle that enjoyed widespread circulation. Irenaeus wanted Marcion to exist. He is takes the place of a shadowy figure called 'cerdo' (= fox) who is also known to near contemporary Jewish literature. The fox was crafty and crafty wisdom was 'fox wisdom' cerdaleophyon.
Notice that the story of Marcion's repentance is closely paralleled with that of his predecessor:
For Valentinus came to Rome in the time of Hyginus, flourished under Pius, and remained until Anicetus. Cerdon, too, Marcion's predecessor, himself arrived in the time of Hyginus, who was the ninth bishop.(5) Coming frequently into the Church, and making public confession, he thus remained, one time teaching in secret, and then again making public confession; but at last, having been denounced for corrupt teaching, he was excommunicated(6) from the assembly of the brethren. Marcion, then, succeeding him, flourished under Anicetus, who held the tenth place of the episcopate.
Clearly then you can believe what you want to believe. If you want to believe that there was a real Marcion who was a heretic up until the time of Anicetus and then - with the coming of Polycarp - was rebuked and then tried to join the Church but kept falling away - as the Prescription says 'because of his overeager imagination' and then was excommunicated only to reach a deal that he would bring in his Church into communion and then died - that's your privilege but most people it is a development of what appears in Adv Haer 3:
https://books.google.com/books?id=9zgMA ... ed&f=false
My take is that Marcion is a late edition to the narrative. Notice Marcion doesn't even figure prominently into the main narrative of Book One. As is commonly acknowledged Irenaeus's apostolic succession list derives from Hegesippus where the place of Marcion is occupied by Marcellina. The switch seems to have been preceded by an addition of 'Cerdo' who takes on all the Marcionite attributes in Pseudo-Tertullian's Against All Heresies based on Irenaeus. It gives Marcion only a line and adds "he attempted to approve the heresy of Cerdo; so that his assertions are identical with those of the former heretic before him."
As Marcion's role became more prominent the story of Cerdo's excommunication became more developed and included all the details you accept about Marcion. Indeed it is worth noting that κέρδος properly means "gain, profit, lucre" so even the story about buying the church with two hundred sesterces goes back to Cerdo. Indeed the origin of a Marcionite heretic with this name might well come back to Philippians:
For to me, to live as Christ (ζῆν Χριστὸς) and to die as gain (ἀποθανεῖν κέρδος). Yet what shall I choose? I do not know! I am torn between the two
Could certainly be read as if the speaker was named Cerdo perhaps the origin of the heretic of this name.