Not getting back with baby's father for a girl?

My son's father has been extremely emotionally abusive to me the past 2 and a hald years of our 3 and a half year relationship. He would also get physical if I would threaten him or push him. He has done countless of heartless things to me e.g throwin my bag out the car while I was 8 months pregnant, pushing me on the floor, cursing me out in front of people and most of allthe mind games! But what makes me stay with him is the fact that he says he loves me and he hasn't cheated on me. Although we broke upp for three months we got with other people, then got bk togvether. So he got out of a county jail he ws in for 3 mo. And went right back to being an asshole. So we haven't been together since. But the other day he left a big bouquet of flowers and talking to his grandmother I found out he's been working 13 hr days everyday since! She said he wants to come back to me with a stable life and a place. But I'm falling for this girl who is so geniune and she fulfills my emotional needs like no other man can ever. And I am such a sentimental,emotional girl! She also accepts the fact I have a kid...what do I do? Please helpp. I want to be with this girl but is that selfish to my son for not being with his father? Btw. Out of 12 mo. Ki was a single mom for like 7-8 mo. Too much stress..no help fcrom family or him. I am only 19 btw!