*thought more about this*
Hi Joe,
The underlying issue is that by trying to control you via curfews & college dollars, your mom is trying to get rid of the gay part of you.
And while I have no doubt that you can be successful doing this on your own, you have a right to those college funds just as much as your brother and sister do. You've worked hard at being a good student and you deserve the opportunity to go to the best schools possible.
If possible, have a sit down with your mom (and maybe your father too). Tell them what you've told us. Tell them that you will be going to school with or without their help. Tell them that you've earned the right to stay out later, that you've maintained excellent grades, work hard, and deserve their trust. Keeping you home at midnight on vacation will not prevent you from having desires for companionship of the same sex. It may prevent you from fooling around with boys (and girls), but the thoughts won't go away.
I'm not sure you should come out and threaten them, but they need to understand that they risk loosing you if they continue along this path. Do they really want to risk loosing a good relationship with their son? Put it in those terms.
Vic