Custody?

So I'm 9 weeks from having my 3rd child (1st with my ex) and he said if we ever split he'd go for 50/50 custody like he has with his daughter from his ex wife. Well he broke up with me so I'm pretty sure this is what he is going to do. My question is how does that work? I've never had to deal with custody agreements before. We were never married. Will he still have to pay child support? I just want to know how that goes for anyone who's been through it. I'm in Florida btw.