Have you tried meal planning and shopping together. Find some time to plan out when he will be visiting for the week and what you both want to cook for dinner. You can either shop together or ask him to do the "couples shopping" for the week so the burden is on him to pay and you to pay him back if you fee like it.

As far as the table manners, you are going to need to work with him on that. It is not acceptable or cute to start eating off of another person's plate. He needs to learn some boundaries and self-control.

You may want to talk to him about how he ate as a child. He may have grown-up with food scarcity, or a parent who pushed food on him, or any number of other events that could have be driving this behavior.