Congratulations Rain on your baby girl.
I think you need to love bomb your boys. Get them involved in baby matters, tell them how proud you are of them, how they'll be good big brothers.
I see a fire is starting to be lit in your belly. You are strong, you left this asshole! You picked yourself up again, found a better love and have another baby who is going to be loved by you all.
You can do it Mama! But you really really need to dig deep and change your thought behaviour. Forget him for a second he's an abusive man and you can't change him into anything better. But you can change the way you react to him.
The abortion/adoption idea is definitely you catastrophising. You are having an awful time I have no doubt but you are thinking extremes and you will make yourself ill with this thought pattern. Not a real Mum also is extreme thinking too!
I think CBT could do wonders for you if you can access that?
Write on a big piece of paper what things you have in your life that make you happy. Your children, your fiancé, the home you've made together? Your job?
Then write how each of your children and fiancé make you feel and stick it in your bedroom somewhere where you can see it each morning.
Another thing my CBT therapist taught me to do (which I love!) Is called "Faking it til you make it"
Be confident with everyone like confidence seeps through your pores. I know it's difficult but you really need to dig deep, this isn't easy but it's extremely worth it!
Shoulders relaxed, back straight and eye contact. No explanations or compromised with your ex just to the point sentences.
Let your ex and especially your boys know that their behaviour is unacceptable too. "XYZ is unacceptable behaviour and it won't be tolerated in this house. We are kind and considerate of others"
Good luck on your journey to happiness OP