Sounds like a cop out, to me, on his part. There's no reason for him to not address himself in therapy, not just for your sake, but your child.
I'm reaching a point in life, that leads me to feel that it's oft those unwilling to seek help that contribute to the unwellness of others, yet so quick to point fingers..

If he had, or would come to seek any understanding of your mi's, communication could turn for the better. Each of you could pinpoint what sets the other off, in order to create a more peaceful/calm/tempered environment.

For instance, with bipolar alone, knowing that sleep/rest helps keep you at a level emotional place, he could(referring to your other thread) ease your burden in parenting to let you regroup and feel ok.

Of course, it looks like you are making attempts to understand what you go through yourself. Not everyday will be perfect, but without a stable coparenting situation, how are you expected to have the better days that offset the off days?