He had mentioned the health care cost to a client. I suspect he didn't realize that whatever KB paid for Baby K's health care as a full time employee of Doss, it was likely much less than he would be paying on the direct market for similar coverage.
What happened to Mr. Big Stuff who promised her that if she came to Colorado, he could support her? I think he made some kind of bad financial decision and was probably furious when she 1) got pregnant (like he had nothing to do with that, either time) and 2) bought a condo instead of putting the money towards his bills or a ranch for him.
Don't forget, he also owed KK money. IIRC, at one point she testified she had lent him money - 'thousands', although that could mean 'only' a couple thousand. I don't know if that was the money he owed her for the horse they bought together. I doubt that her ex-husband ever knew about that debt.
There's no doubt in my mind that he couldn't have afforded his lifestyle if Ma Frazee kicked him off the franch. Not unless he could find a well-heeled compliant woman to foot the bills - and take the abuse.