Even though I don't believe in God, I think your lyrics are very, very good and contain a lot of truth.
I think that your decision for the piano is a good one. When in doubt, use a piano with an acoustic and call it a day
From the mix, I think the darker BG vocals clash with your vocals in some places at the end, maybe they can be panned more to the right. But the rest is really good and well balanced.
PS: in the text above you forgot the "the" in
"is damned sure keeping the score"