Not going to repeat my discussion with him, but I preemptively answered all of those objections with the apologetics site guy, and he like you was not ready to see them taken apart. And the verse does not preclude dietary or any other thing simply because it makes you uncomfortable, Jesus left it wide open. And your single-verse objection - besides being so general it can't possibly be defensible - would deflate a great many things you claim to believe in, simply because it's not possible for every verse to have an echo everywhere else.
I'm not going to prove everything to you here for reasons I won't explain, but suffice to say you've just seen several of your certainties have the rug pulled out from other them, which should instruct you to think. He that hath ears to hear, let him hear.