1. I don't even know that becoming a Protestant is the right answer, but there are a multitude of progressive, Christ-based churches that will allow you to dabble in whatever cultural relativism will suit your fancy.
2. Do we have any evidence that Biden, as a Democrat, is personally against abortion but sees it as a bridge too far politically? If you think of abortion as the Catholic church wants you to think of it, as murder (e.g. would you hire a hitman? - Pope Francis), you can make some inferences based on behavior, I think.
Regardless, you seem like you have spent a lot of time in study of theology or history of theology or whatever-- do you care to opine on why a Catholic would remain a Catholic instead of going to an alternative and more welcoming religion to their beliefs?
Also, why can't a Roman Catholic just become a Protestant? The logic would seem to be self-sustaining and circular in that "I used to think I was a Christian and was a Catholic, boy is my face red-- I was duped and not a real Christian at all! Now I'm a Protestant and both get to have progressive cultural views and be a Christian, glad I saw the light!"
I mean this is the same argument Brisket and other reformed Republicans have been giving in just the past few days on how they used to be Republicans but now see the light as non-Republicans.