I think, coming from a broken home...
Your husband needs everything reevaluated. You are growing resentful, and he bends to her every whim. I'm sorry, but it seems he is still under her control. Sometimes you gotta be the squeaky wheel. My mom was a single parent, my dad was the other weekend dad to my brother- yadada. We had 3 sets of families to deal with. Well 4 actually. None of them worked the way you describe. None of them ranked higher than others. Everyone split everything and pick ups/drop off were outlined in custody papers. Sounds to me like she needs someone to step and say, okay, we need a new plan.
And I'll be honest. My family is very very broken. My parents are each on their third marriages. I
Have 3 siblings and not one of us has the same two parents.. BUT at my wedding???? Every single person was there.
My brothers mother and her husband (we share a dad)
My older sisters dad and his wife (we share my mom) they also brought their two daughters
My younger sisters dad and his extended family (we share a mom)
It can still stay functional and friendly. But part of that was, people go everything in writing. Even down to who paid sports. Nothing was ever really an argument. And the kids really benefitted.
BFing, CDing, all natural mama to three boys! Certified lactation Counselor