How do you get somebody to stop liking you? I want to be friends with him, but I can't handle any of this. This being the feeling of paranoia I get when I talk to him, out of fear that he'll misinterpret friendliness for romantic interest.

Well truth of the matter is, and I know you're not going to like this answer, but you personally, can not do anything to get some to stop liking you (unless you really want to do something societally or morally frowned upon, but then you'll have to live with the consequences of your actions which is a jillion times worse to deal with than unrequited romantic feelings.)

However, if you do want to be friends make sure he knows and understands CLEARLY that you don't want to be in a relationship now or the new future.

Also, you don't be to pushy in regaining the previous friendship (he'll probably misinterpret your friendliness) but try to not isolate or ignore him (then he'll probably feel like you're trying to eradicate his presence in your life.)
I know finding that balance isn't easy especially when things start easing up between the two of you, but keep your head focused and just keep an eye out on small characteristics that hint at him trying liking you again. If he does, then you need to lessen the amount of friendliness you show him.

I'm so sorry this is so long; I have far too many things to say for such a small text box ahah.