I'm sorry if you thought it was a straw man. I think we may be talking at cross-purposes.
I agree that a miracle, though intrinsically implausible, becomes more believable when there are trustworthy witnesses to it. Was that the point you were trying to make? So assuming we can trust St Paul, we can trust that he is right about the 500 witnesses, and that these witnesses were trustworthy. But some people may not be so predisposed to trust St Paul. They might argue that, whatever his personal revelation may have been, he was predisposed by that experience to believe others who were claiming to have seen the Resurrection, or even to exaggerate the number of witnesses. After all, they were no doubt making the same claims earlier, when as Saul he was persecuting them. While before he was predisposed against them, after he became predisposed in their favor.
There is no reason, in other words, to believe that the testimony of these witnesses itself brought about his conversion, and so we have to fall back on St Paul's word that these witnesses did exist and that they were trustworthy. It all hangs on what we believe about St Paul. You say we have no reason to doubt him. I would say that it would be inconsistent with our faith to do so, but anyone who does not share our faith could probably find several reasons to doubt him. He may have interpreted some neurological problem as a supernatural sign, and then read all sorts of things into that. After all, he already showed evidence of a religiously zealous and extreme mindset, and we all know examples of people who were enthusiastic Baptists becoming enthusiastic Orthodox, or whatever you like.
Going to Genesis and the Flood, I agree that even knowing who the author was is problematic. Tradition says it's Moses, modern scholarship says it was a nebulous oral tradition. Of course, to an Orthodox believer, nebulous oral tradition can carry the weight of authority; exclusive reliance on written testimony is a Protestant thing. But whether or not it was by Moses' hand, we do believe it was inspired by the Holy Spirit. This doesn't mean we have to interpret it literally, but it does mean that whether or not we interpret it literally is a question of hermeneutics and our understanding of the patristic consensus. It is not consistent with our faith to doubt that Genesis has any truth value, but only to consider at what level this truth obtains.
I still submit that every miracle requires special pleading, because in every case, we have to believe supernatural intervention overrides ordinary natural laws. This goes for either the Resurrection or the Flood. It is true that, as a global event, there are a lot more potential areas where evidence for or against the Flood may be expected, hence the whole problem of reconciling the Flood narrative with the geological evidence. With the Resurrection, pretty much the only place where we would expect evidence for or against it is the tomb itself. As we know, even there we have a plausible alternative explanation: the disciples stole the body. Whether we accept this explanation or accept the Resurrection again depends on our predisposition.
Some of what you say about Genesis obviously takes modern biblical scholarship and archeology at face value: that it was written to counter pagan myths, that it was not written as a historical narrative, that it relied on oral tradition. All this may be true, but if we're going to accept the secular scholarship so uncritically on that count, why should we not do so where it raises questions about the reliability of the Christian tradition?