Can mu husband sue for custody and win?

My husband and me are getting a divorce, well i plan to file, the problem is he says he will fight tooth and nile to have our son not because he wants him he tells me but because i deserve to be alone (nice dude right?) well heres what i have hes an illegal alien in the county, he drinks heavily and uses drugs and has had numerous affiars, he also has been emotional and verbally abuse much of our marriage, i married at 18 he was 25 and i feel like i want to be truely free! but i dont want to lose my son.. can you please tell me if its a possiblity?