Why do i bother sometimes?...(update**)

So I’m the cook in the house because it’s either that or we don’t eat or argue. I’m perfectly fine with cooking and trying new things. Here lately we get his son on the weekends because he lives with his mom. Anyways we actually moved to Pennsylvania to be near him in February. Every weekend is the same routine. We cook breakfast, sometimes lunch and always cook dinner. His son WONT EAT what I COOK FOR DINNER. This didn’t bother me at first because i thought “ ok I’m still learning maybe it’s not good” but it’s an everyday thing when he’s here. He will sit there and fight with us even over cooking food that he likes. It’s driving me crazy because i go out of my way to spend that little bit of extra money that we don’t actually have to spend on these extra groceries for him. So i make his favorite food and he sits there and picks at it and takes over an hour to eat food that me and his dad eat in about 15 minutes depending on the portion. We give him a decent portion because he is also on adderall. He doesn’t take it when he’s with us most of the time but he still doesn’t eat. What am i doing wrong????

UPDATE #1: So today i cooked dinner again since l again am the cook in the house. My boyfriends son actually ate it all. It was something new too. Something he has never had and I’m very impressed that he ate it. I made some stir fry (he loves veggies) and a recipe my mom gave me for lemon pepper tuna tacos. He didn’t even take an hour to eat it either. Only thing we really fought with was him getting stuffed when he had two bites left (3&1/2) for him since he takes tiny baby bites. It gives me hope that as i try new things he will actually maybe eat it.