Why drag your son down?

If he needs less courses a year, then so be it. If it takes him longer to graduate to get where he wants to go, so what? That doesn't matter. People start university/college at all sorts of ages.

What matters is for him to have the opportunity to do what he wants with his life. Taking away options isn't going to do that for him.

It makes total sense that he needs things to be a bit slower right now. If you've been homeschooling him then he's certainly behind most of his peers. (I say that as a teacher - very rarely do homeschooled students keep on par with their peers... People can homeschool if they want but there is sorta a reason why teachers get specific degrees and qualifications...). Throwing him in and expecting him to thrive automatically isn't fair, nor is it fair to limit him.

You'd rather have his teacher be an *** than give up his free time to help your son? Really? I'm sorry, but his teacher does not need to do that - he's offering because he cares about your son. If that makes things harder for you then you should really consider your priorities. If this teacher is willing to take time out of his own life (and also taking away time he might be spending marking, etc) and making his own life harder, you can surely do the same.