The point here Giuseppe is that you are ignoring the nature of the problem. There are no final answers here. The Marcionite text is not known. There is just a consistent silence with regards to the baptism of Jesus by John and this statement in Tertullian:
Whence, too, does John come upon the scene? Christ, suddenly; and just as suddenly, John!337 After this fashion occur all things in Marcion's system. They have their own special and plenary course in the Creator's dispensation. Of John, however, what else I have to say will be found in another passage.339 To the several points which now come before us an answer must be given. This, then, I will take care to do340 ----demonstrate that, reciprocally, John is suitable to Christ, and Christ to Joan, the latter, of course, as a prophet of the Creator, just as the former is the Creator's Christ; and so the heretic may blush at frustrating, to his own frustration, the mission of John the Baptist. [5] For if there had been no ministry of John at all----"the voice," as Isaiah calls him, "of one crying in the wilderness," and the preparer of the ways of the Lord by denunciation and recommendation of repentance; if, too, he had not baptized (Christ) Himself341 along with others, nobody could have challenged the disciples of Christ, as they ate and drank, to a comparison with the disciples of John, who were constantly fasting and praying; because, if there existed any diversity342 between Christ and John, and their followers respectively, no exact comparison would be possible, nor would there be a single point where it could be challenged. [6] For nobody would feel surprise, and nobody would be perplexed, although there should arise rival predictions of a diverse deity, which should also mutually differ about modes of conduct,343 having a prior difference about the authorities344 upon which they were based. Therefore Christ belonged to John, and John to Christ; while both belonged to the Creator, and both were of the law and the prophets, preachers and masters. Else Christ would have rejected the discipline of John, as of the rival god, and would also have defended the disciples, as very properly pursuing a different walk, because consecrated to the service of another and contrary deity. But as it is, while modestly345 giving a reason why "the children of the bridegroom are unable to fast during the time the bridegroom is with them," but promising that "they should afterwards fast, when the bridegroom was taken away from them,"346 He neither defended the disciples, (but rather excused them, as if they had not been blamed without some reason), nor rejected the discipline of John, but rather allowed347 it, referring it to the time of John, although destining it for His own time. Otherwise His purpose would have been to reject it,348 and to defend its opponents, if He had not Himself already belonged to it as then in force.
Unde autem et Ioannes venit in medium? Subito Christus, subito et Ioannes. Sic sunt omnia apud Marcionem, quae suum et plenum habent ordinem
apud creatorem. Sed de Ioanne cetera alibi. Ad praesentes enim quosque articulos respondendum est. Nunc illud tuebor, ut demonstrem et Ioannem Christo et Christum Ioanni convenire, utique prophetae creatoris, qua Christum creatoris, atque ita erubescat haereticus, Ioannis ordinem frustra frustratus. [5] Si enim nihil omnino administrasset Ioannes, secundum Esaiam vociferator in solitudinem et praeparator viarum dominicarum per
denuntiationem et laudationem paenitentiae, si non etiam ipsum inter ceteros tinxisset, nemo discipulos Christi manducantes et bibentes ad formam discipulorum Ioannis assidue ieiunantium et orantium provocasset, quia, si qua diversitas staret inter Christum et Ioannem et gregem utriusque, nulla esset comparationis exactio, vacaret provocationis intentio. [6] Nemo enim miraretur et nemo torqueretur, si diversae divinitatis aemulae prae-
dicationes de disciplinis quoque inter se non convenirent, non convenientes prius de auctoritatibus disciplinarum. Adeo Ioannis erat Christus et Ioannes Christi, ambo creatoris, et ambo de lege et prophetis praedicatores et magistri. Sed et Christus reiecisset Ioannis disciplinam, ut dei alterius, et discipulos defendisset, ut merito aliter incedentes, aliam scilicet et contrariam initiatos divinitatem. At nunc humiliter reddens rationem quod non possent ieiunare filii sponsi quamdiu cum eis esset sponsus, postea vero ieiunaturos promittens cum ablatus ab eis sponsus esset, nec discipulos defendit, sed potius excusavit, quasi non sine ratione reprehensos, nec Ioannis reiecit disciplinam, sed magis concessit, tempori Ioannis eam praestans, ut tempori suo eam destinans, reiecturus alioquin eam et defensurus aemulos eius, si non ipsius fuisset iam quae erat.
As Harnack puts it "in [Marcion's] view, Christianity has no connection whatever with the past, whether of the Jewish or the heathen world, but has fallen abruptly and magically, as it were, from heaven."