good for you!!!!

Personally, I feel that you have made a very, very wise decision. 

I echo Blue Rose's suggestion to document, document, DOCUMENT.  Yeah, the escalation in her behavior may be due to her hormonal imbalance during pregnancy, but she was like this BEFORE.  If she's meeting up with other men while she's this far gone in her pregnancy and you're still living with her, this is never, ever, EVER going to improve for you, or for your precious baby.  This gal is a problem to anyone that she comes into contact with - male, female, or infant.  By documenting everything from threats to hooking up with men at this stage of her pregnancy, it will NOT sit well with Family Court.  She doesn't sound fit to be a parent, a partner, OR a pet-owner!

If it were me, I'd get the legal wheels in motion yesterday, whether or not anybody else approved.  It's not THEIR burden to bear and not their place to stand in judgment.  If I felt that I had to remain until the baby was born, I'd do that solely with the intent of taking my infant WITH me when I either left, or kicked her to the curb.  I'd be documenting everything using exact quotes, dates, times, and facts, and avoid the temptation to add my personal views or emotions - strictly the facts, and nothing added.

Good luck to you, and post back.