I hope it’s okay just to point out that part of this may be cultural differences? The age of consent is lower in Croatia (15) and not sure where the OP is from but it’s generally lower in Europe, I think that may have quite a bearing on attitudes to relationships and age gaps.

I don’t personally see great problems with what the OP is describing if he’s no longer anything to do with her education (he wasn’t her teacher). I do remember having flirtations and crushes with men his age when I was her age. I just found older men more interesting!

It’s very true what OE says about emotional development however, and that’s something I’d be very aware of. Apparently our brains aren’t fully developed until 25.