It's easy to say she's being selfish, but while you've couched this in terms of what's best for your son, it doesn't matter to a young kid what part of the country he lives in, his parents' financial situation, whether they own their house, whatever. Meanwhile, she's being asked to forgo her ambitions because of your mother, your career, your house (I note that you said YOU own the house, not that the two of you own the house)...well, I can see where a woman could feel trapped. Now, maybe she's a raging narcissistic beyotch and doesn't deserve any sympathy, but based on the bare-bones facts you've laid out here, it's very easy to fill in the blanks and picture a situation where a reasonable person would be unhappy, especially considering that none of the things tying her to your geographic location and your personal goals (mom, house, your job, etc.) are likely to go away any time soon, and there's no indication in your post that you'd be okay with her going away to school while remaining married. In these modern times there is no inherent requirement that being a wife and a mother means a woman has to give everything else up, or subsume herself to her husband's career and family, but it sounds like you're not considering option but that or divorce. And given that you're talking about how if you didn't have a kid you'd be divorced already, she'd have to be nuts not to be thinking about what she need to do to establish her own career rather than being dependent on yours.
So maybe a divorce would be a good choice for both of you, but based on what you've said, I hope if you do decide to divorce you can do that without making her the bad guy.