I have no problem with anything you typed or copied & pasted.
My only problem is what does the GOP do when aspects of its platform lose popular support?
What specifically is the pro life movement's plan if a country increasingly accepts legal first trimester abortions, for example? The answer has to be practical - losing political power doesn't advance any agenda in a meaningful way for conservatives.
I don't agree with you that the abortion issue is swinging more towards the Dems, but I'll answer as a theoretical.
In such a case, the Republicans can make a strategic shift towards the Center/Left in the hope of picking up enough swing votes to cover the loss from the right.
I don't think it will work, but they can try.
What I suspect will happen is such a situation will be another Bush Sr. "Where will they go?" -> Ross Perot moment, giving us once more a nightmare Clinton presidency.