I've been away from the Depression Board for a while, and I was quite dismayed to hear how things have progressed. Your wife has a chemical imbalance, she cannot be delt with like a rational person. Her refusal to participate in any additional psychiatric help demonstrates this to a tee. CBT would be of no use to your wife, since she doesn't think she has a problem. Her distorted view of how life will be after getting divorced is irrational. If she doesn't voluntarily get help for her imbalance, you should not even consider joint custody. Frankly, I think you should try to get her committed, and force her to get help. Tell her therapist that her behavior has become dangerous to the children, especially the little one. I wouldn't leave her alone with the baby for even a short period of time. Bi-polar people can become delusional or psychotic, and if not on medication, they can snap at any time. I've seen it happen with my cousin and an old friend.
Face it Rick, you are fighting a losing battle, and if your wife won't take the appropriate meds to allow her to function normally, you need to surgically cut her out of your life. Sever all connections completely. Neither you nor your children deserve a messy, drawn out process. Cover yourself financially, cancel any joint credit cards. Take her name off any joint bank accounts. DO IT NOW. Don't let her clean you out financially, and don't believe for a minute that someone in her frame of mind wouldn't attempt a big money grab in a heartbeat.
I don't mean to sound harsh, but you've been beating your head on this rock far too long. Good luck and keep us updated.