Hi OP
My heart does go out to you - What a really difficult and upsetting situation to be in. No-one deserves this. But equally, how strong and grounded you are, refusing to be dragged down completely and reaching out for a hand. You actually deserve huge praise.
Although incredibly empowering, deciding to leave someone is a huge decision and if nothing else at the moment, I would recommend ypu seek support and lots of it. Use supportive friends and family members. Speak to your GP and perhaps seek out some counselling - Depending on on your age there are sometimes charities who can provide a (sometimes) quicker route into talking therapy.
You seem to be surrounded a lot of negativity because of the way you are being treated and you may need to counteract that negativity with positive people and positive thoughts.
I just wanted to touch on also, your concerns about bonding with your unborn child. We are, of course, all very different - But for me, I didn't bond with any of my children until after they were born. In the first case - not until she was a few months old (14 years later - I still feel pretty crap at times about that). With my second, it was love at first sight and with this one (due -4 days ago), I seem to spend more time worrying about him than I do thinking about bonding - Something I will regret later, I'm sure! In all three cases, I was almost certain that the bonding process would pan out differently to the way it did - So sometimes it's best to just play these things by ear and, more importantly, not give yourself a hard time about it too 
Ultimately, I would say to:
- Take each day as it comes - Don't worry ahead of time too much.
- Find a little happiness in each day. If it's difficult, write it down (ask yourself: what went right today, what was good, what am I grateful for). Eventually, if it's the right thing - you'll add your boyfriend on to this list for helping to open your eyes to what you truly deserve - Because 1. You found the strength to leave or 2. Because you made it clear to him that his behaviour is unacceptable and he changed - Rare but does happen).
- Build up your support network.
You sound sensible, so I am sure that with the above you would eventually do whatever it is that is right for you (and bub, of course).
Wishing you all good luck 