What a tangled web !!
I think you need to stand back and look at the situation as an outsider.
As Ive said before people check the background of a second hand car more than they check details of a partner.
It would appear that you met someone with considerable baggage and that baggage is somehow becoming your responsibility.
Bells ring when pressure is being placed by someone with a poor credit history and has found a decent person to fund them. Thus you are getting the pressure to buy/get a bigger house. Well don't.
Blood is thicker than water and Im willing to bet that you ending up losing all you have worked for.
If her attitude is ,as you describe, before you get together imagine what controls you will be subject to if you live together. Doesn't even bear thinking about.
Bells ring very loudly when I read that there has been no contact for 4 weeks as when people love each other nothing will keep them apart even if its just a daily phonecall.
If you do intend to get together both of you must get rid of your baggage (time will be needed for the kids to grow older).
I have the feeling that the baby was designed to lock you into something that will be hard to get out of.
Well if we forget the financial implications it is all about being protective. As you say you have supported her through the 30 weeks but that support is also for your offspring. You will be able to read many posts on here you will find many men fighting to see their offspring. They couldn't give a rats **** about their x !! But the kid is a different situation. Most men would not like to see their offspring brought up by another man.
And thats besides the future claims on your estate when you demise.