I haven't read the entire thread, but the Founders never intended a separation of Church and State, not even Thomas Jefferson despite his 'wall of separation' metaphor in a letter to a colleague. All were pretty sure the Constitution would work only for a religious, moral, law abiding population.
John Adams once said, “Our Constitution was made only for a moral and religious People. It is wholly inadequate to the government of any other”.
What the Constitution intended was that no religious group would be able to control government to the point that it could use the government to force people into obeying any particular religious doctrine or dogma or forbid the people from any professed belief, doctrine or dogma. The early Congresses not only had regular prayer doing government business but sometimes held church services for the members. Those people fully expected religion to be a present and visible part of people's lives, all aspects of their lives, most especially those to whom it was important, but no power is given to them by the federal government to require anybody else to believe what they believe, profess, express.
It is as wrong to forbid that creche on the courthouse lawn as it would be to forbid a Star of David on Yom Kippur or any other religious symbol on a high holy day(s) of whatever religions are represented in a community if a particular group wanted to place such there.
Abortion is a matter of religious conscience for some, and a matter of principle for many others having nothing to do with religion. Separation of Church and State really doesn't factor into that much at all.