Perhaps there should be, or st least there should be discussion about how IVF is accomplished. But the fact that there is IVF the way it is has absolutely no bearing upon the morality of abortion. We need to understand the distinction between practice and principle.
IVF requires implanting many embryos, in the hopes that one will take which in some cases will then require abortion for the extra ones. The moral question remains in that scenario... I don't see how you can look at it any other way.
Miscarriages are a natural event. Perhaps there should be more research into what causes miscarriages and more should be done to prevent them. But again, that has nothing to do with the morality of abortion.
No, they are not all natural. We can prevent great numbers of miscarriages, but intentionally choose not to do so. One distinction is omission vs commission, but the ultimate moral issue remains.
I do however agree that a truly natural miscarriage, rather than one brought about due to the actions of fallen man, is vastly different than an abortion of convenience.
Do you have some supporting argument for why you reject P1? I’ve never heard a Christian deny P1 before. Ever.
P1 must be denied if it is dependent upon P2 as a fertilized egg may or may not become a single human being. The Chimera issue throws a major wrench into the works, and as such, ensoulment cannot occur at fertilization, unless a soul splits into 2 unique parts, and/or our souls are prexistent. In either case we end up in a big theological mess. Furthermore without ensoulment, does a human being exist, or is the fertlized egg more like mere animals, like our genetic ancestors Bonobo's or chimps? This too presents a huge mess, albeit we can look to the teachings of Augustine for some guidance.
P1 in isolation is fine and I do agree with it, ie, a living breathing baby is created in the image of God and possess inherent moral worth and value. Some Jewish teachings hold that ensoulment occurs at first breath, and there is scriptural support for such... but it is far from explicit. As such, to take a safe path, some will roll the time of ensoulment to a period earlier in the development cycle... but how far back it should go is an unknown. What is interesting is that Augustine held that abortion even if it were in an "animal" or "plant" state pre-ensoulment was immoral. In the mid 80's I knew how he got there, but those memories have long since faded. Which again is why I suggest looking to Catholic tradition to help with your arguments.