"Honestly don’t know where I went wrong. Right from the beginning I lay down the law and said I’m not looking for a father for DD nor anything else from you. I’m totally independent. just want a normal adult relationship!"
I think there are confusing elements to your situation and tbh I'm not surprised if your BF is feeling confused and a bit desperate. You do already have a DD and you decided to make a sibling for her; although you were going to live in separate houses, how was it going to work for your elder DD when her younger sibling has a father on the scene but she doesn't? Also, how can you go from trusting him enough that your new baby would shuttle between your two households so that he would have sole care of the new baby for a significant amount of time to not trusting him at all?
What you were proposing with him was not simply a normal adult relationship but something much more committed, involved and complicated.
I'm not sure how easy it would be for your DD either as she got older: if she sees that her younger sibling has has a father-type bond with this man but you have expressly excluded her from any similar relationship with him.
I seem to be more or less alone in this reaction, but I think his instinct of wanting to bond with your DD and build a close relationship with her as well as the child which is biologically his own is natural and healthy. And that it would be hurtful for her to have a situation where her younger sibling has a father figure but she's excluded from that family dynamic.
Your elder DD is still so little that you probably can't imagine her becoming alive to the dynamics I have described above, but believe me, from about age 3-4 onwards, she would start to notice that there was a man who was around her mother and her younger sibling a lot of the time, but for some reason her mother won't let her have a close relationship with him.
Pregnancy is a very emotional time and ideally not a time for serious life-changing decisions but of course the decision of whether to continue with your pregnancy or abort it has to be made now. I'm pro-choice but I still think having an abortion is a very difficult thing to do and fortunately I've never faced having to do so but I have one or two friends who have. It was the right thing for them at the time and they don't regret it. You somewhat rushed into this pregnancy and having this man's child certainly will bind you to him for life and he will clearly want to be involved. So you need to decide whether you can face that or whether you need to disentangle yourself from him.