You've gone from having guilty feelings about being attracted to a former student, to then hanging out with him.
Then you tell him you're gay, and he's cool with it. So, no stress about you being gay.
THEN you decide to "go for it," - even though he's given you absolutely NO SIGN he's interested in you in "that way" and all of a sudden you're speculating that "he just needs more time."
WHAT IS YOUR PROBLEM? The guy wants to be friends, and - despite your exhortations to just take it as it comes - it becomes clear that you want to ignore that he's straight and suddenly it's this:
"I then got it out of him that he needs the time to shift the relationship from what it used to be (as teacher/student) to something else. Although he said he likes that we’re building up this new rapport so far with messaging. Maybe it’s bullshit, maybe it’s not. Part of me thinks if he was really into me, he’d put in more effort."
HE'S NOT INTO YOU. HE NEVER WAS. You're simply someone who was a part of his adolescence and now he's seeing you on a more equal playing field.
Except it's not, since you don't listen to what you're told.
You have boundary issues. When someone says "NO," you don't push or try to manipulate them or the situation. You don't start speculating about "...if he was really into me, he'd put in more effort." WHAT?!?!? He sees you as a social acquaintance. Not a close friend, but someone he keeps in touch with. He's been entirely consistent about the boundaries. You? You just want to push those boundaries out of the way, all because you can't accept that someone isn't available to you in a sexual way. If he were a woman, and you were interested, you wouldn't push it, because with #METOO, you'd be concerned about harassment. But since it's only a gay man, (and we're all men here, right??) you feel that respecting someone's DISinterest is a road too far to travel.
Grow up. Leave it alone. And leave HIM alone, because your interest in him is not about him and simply having him in your life, it's about YOU and your desires for him. That's nothing more than selfishness. He doesn't need a secret predator in his life; he just wants (maybe) a friend. And every time you post, you're showing you can't just be a friend. Let him walk out of your spider's web, or you'll do something to alienate him, and then you WILL be nothing more than "that gay guy who kept trying to get into my pants. Oh, and he used to be my teacher, too!"
And if that IS all that you are, he neither needs or deserves someone who is looking at him as someone who'd be into you "if only he put the time in." (Right.) The proverbial Wolf in sheep's clothing.
THAT'S the reputation you want to build???