How about just a cheese sandwich? My daughter doesn't like jelly, so she only eats pb sandwiches or she will eat a cheese sandwich. I have gotten her to eat new things by enforcing the rule that you have to have one bite of the new food every time we have it. She loves brussles sprouts because of this method.
I understand where the school is coming from, but at the same time see your point. My daughter goes to a private school now, and the food there is not only good, but very nutritious. Some of the public schools won't even let you bring in homemade goodies for parties. I completely understand your financial situation. Have you tried applying for foodstamps or any government assistance? I know it isn't something you probably want to do, but it is there for a reason. If I wasn't receiving foodstamps, I wouldn't be able to eat. Also, have you heard of the AngelFood program? They give an entire box of food away for around $30. The food is decent, and fresh. It's not near expiration or anything. I think that with him being on spring break, now would be the time to expirament with new foods or ideas.