There is much much more to this than a mixed orientation marriage!
Yelling at two kids until midnight is, or borders upon, verbal/emotional abuse. Was your son exaggerating? Or did she in fact scream at them for hours? If so. Is this new? Or did this happen before the breakup as well? In either case, it NEEDS to be addressed in counselling, perhaps with the entire family.
It also concerns me that she "intentionally" spent more $ than necessary in order to make it difficult for you to pay the bills. ??????? That is some weird kind of vengeance. Not saying you're perfect and she's all bad, but these are serious problems on her part, and if she is willing to treat you that badly on purpose, rather than communicate her anger to you in a way that allows you both to resolve and compromise, then what is to stop her from using backhanded and manipulative tactics with the kids?
Oh gosh - I need to stop butting in here. These issues need to be addressed, and you are on the right track getting counselling from your pastor and from a therapist. Quite likely the entire family needs to be present with the therapist and/or pastor as well. Make sure the kids have someone they like and trust to talk this out with as well.
I am so sorry all this debacle is going on, for all of you. I hope you will be able to find peace within while things resolve, and wish you the best.