OP, your situation sounds horrendous. It's far more than it being 50:50 though.
In your case the issues arise because you have an abusive ex that is continuing his abuse of you through your DC.
I'm so sorry.
I have my DC all the time. They were very small when we separated. Also a very abusive marriage. The difference is while he wanted to see the DC initially, it was all on an ad hoc, casual basis, no actual parenting. This was very hard when they were small as it meant I never really knew when he'd see them or if he'd show up. They didn't stay overnight until they were much older, and only my younger two did, occasionally. He wanted the fun stuff essentially.
When they got to about 10, he started treating them badly, and they wanted no further contact. They are now teens / pre teens &'have sporadic text contact.
He made this a huge issue in our divorce - alleged parental alienation, I was forced to spend a fortune being evaluated by court-appointed psychologists and so on. Very traumatic. Made no difference anyway.
While I'm profoundly grateful they are free from his abuse, largely, and that I am not in your position, it's very hard being the only parent and having no break & no support. And no life of my own really, bar work.
The ideal is obviously shared access that places the needs of the child at its core & I know of a number of situations where that does happen, thankfully.