This sounds a little like my DH. Especially sharing a dessert… I prefer to take my time and he will eat most of it. I got really resentful of little things like that.
I would make cookies for the kids for the week. They’d come out of the oven and next thing I know, he plowed through5-6 of them in 5 min.
I would cut up veggies for the kids for lunch and he would eat them before the kids did. They were in the fridge the whole time - but he will NEVER prep them himself.
We had enough fights and fortunately he is somewhat sensitive. Of course now, he won’t eat anything I bake and I feel badly. He says he doesn’t know what he can eat. Just recently he started asking me.
He is finally getting evaluated for ADHD soon. I honestly believe this is an impulse control issue (there are tons of other issues - not just these - these are just some of the food related ones).
Now, when sharing a dessert, I will literally cut half or what I want and pull it to my side of the plate. That works.
So while he could be a jerk, it could also be an element of ADHD. Just a thought.