Wow. In just 4 pages of threading, you've decided to abandon the possibility of a marriage to this woman because strangers on these boards gave you advice to pursue your law dreams? Are you kidding me? (No offense to the posters- I'm sure your counsel was very wise), I am just REALLY hoping that the OP was leaning towards ending it BEFORE he started asking strangers to make a life-changing decision for him.
I get that this woman is high-strung (the money, THE MONEY!!! the kids, THE KIDS!!!), and yes, that's probably VERY exhausting, but have you ever suggested going to a financial counselor together and sitting down to show her that the finances will be ok? I'm not married. So, I'll be taking additional loans to live on/pay bills while I'm in school. People do this everyday. It's really not the crisis situation you may have imagined. And, as for the ultimatum- yes, that's tacky of her, but there's an easy way around that. Get married. Have a baby. Change your mind. "I'm sorry, honey, but my heart is calling me to law school. We'll get a private bank loan to cover the living expenses for the next few years, and then we'll be just fine when I get out, cool?" What's she going to do? Walk away from you as a single mom? Why? Because you want to get more education and will eventually be better off financially? No. She'll stay. You'll have it all. Well, you could have had it all if you hadn't ended it so abruptly. Sigh.