Hello globalnomad ,
Welcome, welcome to bpdfamily
I can hear in your post many mixed emotions and a lot going on for you and your SO, not least that your SO is pregnant. There is also a crystal message amidst the difficulties that you have encountered that says that you want to try and improve your relationship with better boundaries.
You have definitely come to the right place, there are many things this forum can help you with around defining, understanding and implementing boundaries. Many, if not all members on here including myself realise that boundaries are important personal tools to keep us ( and in many cases also, our children ) safe and secure from the behaviours that our SO's present with. Behaviours that you outline in your post.
Here is a link looking at what being in a healthy relationship might mean, that also explores the introduction of boundaries;-
https://bpdfamily.com/bpdresources/nk_a115.htmWhat support do you both have other than each other, family, friends, a therapist?
Take care of yourself and keep posting.