Most of the freshwater puffers need to be kept alone or with other puffers of the same species. There may be exceptions to this rule, but in general the tank mates may become an expensive lunch for the puffer
Considering the size a dempsey grows your tank is going to end up to small for him a minimum of 45 gallons as a juvenile if you want to keep other fish you need to think about upgrading your tank
A good side dish would be something you can just open and eat, like chips or fruit. For dessert, f you can heat up some coals in the fire, coat a cardboard box with aluminum foil all over and put a wire in it (like from a hanger) before you go. Then you can put a cake pan full of hot coals in...
... he lives far away. It was a summer camp. I'm sure he has forgotten about you and all those other girls and went back to his regular life. Like you said, you're jail bait for him. It isn't worth it to him.