Uhmmm I'll have a go. :) I'll have to change your first sentence to positive, so you can see how it works. They left some food for me. = You are the reason why they left the food. Who is the food for? The food is for Jessie. My uncle left a large fortune to me. = Well, your uncle would leave a large fortune anyway. He simply decided it should be sent in your direction and given to you. These are very specific examples you are asking about. I'd suggest you look for more examples of "to me" and "for me" and see how it works in the greater picture.

They can be used in many different ways. "I left food for you" = I left food, specially so that you would have it. "He left a fortune to me" = He left a fortune, with the instruction that it should go to me. "He left a fortune for me" is also correct, in a different sense (it implies he's still alive) "I left food to you" sounds strange.