I married the first time at 24 to a lady that was 6 yrs my senior and she had two children. Although we are now divorced, I still have a wonderful rewarding relationship with the two kids and now there is two "grandkids" that I absolutely wouldn't trade for anything in the world. I can't always say I made the right decision or done the right thing but I can say I always had their best interest at heart. If you love the lady, don't worry so much about the kid, that's an overblown argument and the children usually take care of themselves for the most part anyway. They really don't cost much until it's time to pay for the college tuition
and it can be very rewarding, particurly if the father is really as bad as you say he is.