Asklemmy

(I originally put this first para at the end, but it's pretty important, so putting up top) Be aware that just because we're autistic, it doesn't mean we're not bad guys. He might be grooming her, he may already have more personal information than he should, and he may be targetting autistic children specifically. If you think that is the case, go to your parents or the police. I know that's the last thing you'll want to do, but the consequences if he is can be life changing or fatal.

(Original follows) Fellow autist here, if that matters, but probably not.

No, it's not mean. People come and go out of each others lives all the time. Your time with this guy is clearly over - if it feels less than fun or has become uncomfortable or weird, move on. Why not? You don't owe him anything.

As you know, autistic people are no strangers to being obsessive, and putting that alongside a lack of awareness when we're pushing personal barriers, we can be really annoying. I don't recommend you accept any money or gift cards from this guy, even to buy your GF a new tablet. That will give him a bigger feeling of entitlement and certainly gives him power over you.

Just stop communicating. No explanations, no apologies, both of you just stop and block. If he tries to contact you after that, or by other means, that's creepy af and definitely report.