At your ages the 4 year difference is something to keep in mind but probably not a major problem.

You say you respect him, and I think it's important to you that he returns the respect. Part of that respect is respecting your attitudes about sex. To respect your attitudes he first needs to know what they are. At some point - in the daylight, not when you're making out with him in his dorm room at midnight - you need to educate him. Sexual expression spans a spectrum, from holding hands to having intercourse with the intent of conceiving a child. He'll have no problem accepting the notion that various things on that spectrum are (or are not) acceptable to you at various points in your relationship. Come out and let him know that you foresee a time when you will be naked in each others' arms, enjoying post-orgasmic afterglow - BUT THE TIME IS NOT HERE YET. If you can explain the conditions when various activities become acceptable, so much the better. But make sure he understands that his respecting your limitations is very important to your decision to have sex with him.

And then help him follow through. He's going to test your limits, at least unconsciously and perhaps deliberately. RESPECTFULLY tell him "No, not yet.". Gently but firmly move his hand from where it shouldn't be to a better place. And don't hold it against him, or use it as a weapon in arguments (e.g., "You only want me as a sex object.").

You're asking him to do something that is, at his age, difficult for him to undersatnd and harder to do. His body REALLY wants sex. It will help him if you can provide an alternate outlet. If it doesn't compromise your principles, help him hump against you (clothed, or undressed as you think best), use your hands or mouth. This not only relieves the immediate stress, but assures him that you really are working toward a more intimate encounter in the future, and that you're willing to work with him toward mutual goals.