LT-- I hate to say this, and I know I only have a partial picture through the Internet forum, but I believe the dominant part of your situation is your W's mental health. I don't see your marriage getting better until/unless she gets to a better state of mental health. Put another way, even if you were to magically subtract out your marriage and a child from your wife's life, I think she'd still be full of anxiety and confusion, and discontent. Would you agree?
Me: 50, MLC/WW 45 Young kids Nov 2015: BD1 Apr 2016: BD2 Jan 2017: W filed Feb 2017: D final