Document document document EVERYTHING!!!
Go to your family law facilitator at the court house and seek their advice. Mediation will help you to gain custody, especially if you place all these documented situations into declarations. If you have witnesses to his abuse, have them write out declarations. If you children are old enough, have them write out declarations. Legal aid here in California is set up to help those in low income situations...look into it and see if your state has if as well.
Hope you get more advice from others but that is what I am doing on my end...
be strong~
hugs.