SAdly, losing someone may be what makes him realize his wrongs - it's what helped someone I knew in high school/college to finally improve when we stopped hanging out. He wasn't an Aspie but had other issues I'd tried to help him with.
However, one thing you can try is role playing. He may not understand that he needs to treat you like that stranger who he is so nice to - perhaps he has this line in his mind and thinks once he knows someone well he can turn off his "controls" that regulate his voice, tone, etc.. When, inf act, he continues to need to use them, just be more moderate in them. he may have just 2 sett9ings he's learned - "friend" and "stranger."
So, if that's the case, suggest to him that he treat you like that stranger who he is so nice to. Then help him to see how he can turn that "vocal tone" regulation down slowly, without turning it off, and then the other things.
At some point, of coruse, you have to realize it might not work, but this is something i would at least try. Not knowing how much education he's had and how much he knows about AS, he may not even realize that he hs a problem putting himself in other's shoes; he may just think he has one setting for you and another for strangers.
At least, that's a good guess.