Accepting split time. Advice please!

I left my husband last week but haven't officially filed for divorce yet. I'm struggling because our son is 18 months old, and I've always done everything. My husband has changed one diaper, did bedtime on time, has never done bathtime, got up with him in the middle of the night once (he still wakes up multiple times a night), and he doesn't hear him crying during the night. That one time he took care of him was because I woke him up. I could count on 2 hands the number of times he's been alone with our son, most of the time only 30-45 minutes. Twice was for 2 hours and that was his absolute limit. He couldn't handle it by himself anymore. He'd text me "please come home". As a family even, my son and I spend maybe 20 minutes with him each day, sometimes we don't see him at all even though he's home, he chooses to stay outside working on his hobby car. I'm really struggling with the fact that if I file divorce I have to give up time with our son. As bad as he treats me and has disrespected me, I wonder if its better to stay just to not have to battle custody and give up time. I cannot imagine not having him on holidays etc. How do I get past this? Any advice?