Welcome and hello

It sounds like she had a horrific childhood, and no surprise she has trouble with attachment in romantic relationships. It sounds like you, too, have been through a lot, with more to come: having a child while there is an ex BF lingering in the wings, who also has a special needs child. Complicated!
You have a little bit of time to work on communication skills and other things to help ground you before your child arrives. That will help a lot. It's a good idea to investigate your options about how things will go after the baby is born. She may feel overwhelmed and need all the help she can get, and at the same time, her hormones may be on tilt and her moods may fluctuate minute by minute. What can be complicated for people with BPD, and perhaps RAD as well, is the need for help and at the same time resist feeling controlled.
Have you tried any of the validation skills with her? That's a good place to start.