Sorry OP, in the kindest possible way, but why are you putting up with this shit? You're a grown up independent smart woman, just why? You tried talking to him nicely, did you? Well, it didn't work, so time for a FUCK YOU, YOU DICKHEAD convo.
Telling you to ASK HIM before you eat something? FUCK THAT. Makes me so angry to even read it. It's humiliating, he's not your owner/master to throw you scraps from his table and give you permission to eat it. Tell him that and don't mince words, don't put up with this. If nice/normal talking doesn't work, tell him that he's being a twat, a tightwad (with YOUR money), a control-freak, a weirdo and you refuse to listen to him any more. From now on, if he cannot shut up, he buys 2 items of each and you don't give a shit that he 'prefers to share', you want your own tub of ice cream (or 2, or 3, or as much as you want) and you eat whenever you want and as much as you like. If he doesn't like it, he's free to fuck off. And it's not you, who 'doesn't have a sense of humour', it's him who is an absolute idiot. Seriously.
I admit, I'm weird about sharing too. Just don't like eating from the same bag/tub and cannot explain why. I'm not greedy, I just don't like it. But instead of bitching and crying about it, I buy two of each like a normal adult. Everyone's happy.