You keep making the point that the Republican position on abortion is strictly a religious one. While I don't disagree with much of what you wrote, on this one thing I want to point out that for many like myself, my stance on abortion has nothing to do with religion and everything to do with the Constitution and Science. I could care less about the religious argument, other than those who use it have come to the same conclusion I have but through different means.
I think compromise on the issue can be found but you first have to have people on both sides willing to compromise. The biggest problem you will run into on the anti-abortion side is that when presented the fetus is a life, and not a clump of cells, which makes the taking of that life murder. Lee H. Oswald was murdered in cold blood. Everyone was happy about it, but it was still a murder. Once life if applied, then the maintaining of that life is the only reasonable standard to be obtained.
If you wanted a national codification, not of Roe (which is horrible case law) but of abortion then 15-20 is halfway through a pregnancy. If you leave it at those weeks, then:
You would be ok with aborting this baby then.
FYI from what I understand that baby is still alive today.
I could be convinced of 4-10 for a national codification, but with the caveat that states can make that more restrictive as they see fit, but not past 10 weeks.
At 10 weeks you are pushing the limits of what I would consider barely tolerable, not reasonable, and I'm not talking about religion here.