A good diet to feed him would be Oxbow pellets (doesn’t have to be Oxbow, but they’re my personal favorite choice lol. My rabbits go crazy for them.), any sort of hay, and greens. There’s many lists of safe greens for rabbits that you can find. If you’d like, I can provide some of said lists for you. As treats, you can give him fruit (I can give you a list of safe fruits too). Hay should be 85% of his diet, and he should eat his body size in hay per day. It not only helps with digesting food, it also grinds his teeth down and prevents them from growing too long.
I understand it’s easier said than done to get him to eat this, especially if he’s so used to not eating it. The only thing I can recommend is to keep him in a smaller area in order to restrict him from the dog and human food. When he’s in the smaller space, you can “force” him to start eating the rabbit food, as it’s the only thing he’ll be able to eat. If he’s not litter trained, it’d also be a good opportunity to try litter training him, especially since the hay should be in the litter box anyway. Maybe start with an exercise pen, put the litter box in the pen (with the hay), give him 1/4 cup of Oxbow (like I said, doesn’t have to be Oxbow. If you’d like, I can also give you a list of nutritional pellets similar to Oxbow) pellets, and maybe a little bit of lettuce. He’ll have nothing else to eat, and he’ll get curious enough to poke at the food you’re providing him in that exercise pen. I really hope he becomes a healthy boy
I wish you the best of luck because I know it can be very difficult having picky rabbits.
