Custody battle.. will he win?

My ex is talking about taking me to court for full custody. A little background info. We have a 3 year old (4 in August) & a 2 year old. We’ve never truly had a relationship.. just two people living together, taking care of two kids. More so, me than him. He makes close to 80k. House with enough bedrooms for them. He’s only helped a handful of times for diapers, wipes, etc. He doesn’t see them when we aren’t together so this may be weeks or months! I, on the other hand, am with my kids 24/7. I make like $12 an hour & only work 20 hours. I’m in nursing school. I live in a one bedroom house with my two kids. My son sleeps with me & my daughter sleeps in her crib. I only have a shower to bathe them in. Most of the time, I just take them to my moms bc she lives like 5 houses away. I’ve filed two charges against him for domestic violence but both have been dropped. Stupidity at its finest. One was assault & battery 3rd degree & the other was CDV 3rd degree. He’s called me trash in front of my kids, had my son call me trash. None of which I have proof of. He’s told me to kill myself & wished raped upon me (I have emails). He constantly head butts me in front of the kids. (No proof of that as well). I’ve never had a drug problem or alcohol problem. I’m just worried he has more than me. He says I’m selfish & I need mental help. I spent the first year of my sons life laid up on the couch bc I was so depressed. I think I had PPD, but was never diagnosed. He thinks I’m not allowed to have a break from the kids & by doing so, I’m selfish & only care about my needs. I don’t really know what court looks like or how this will go.. I’m just scared that he may take the only thing good I have left in my life! I’ve never kept the kids away from him.. but I have a feeling that if he gets primary custody, this may be the case with him 😭😭