That's really good to hear! I'm so glad he's doing better. I hope you are able to find a vet that can help you out. You may want to just stick with giving him only grass hay for the time being, until he's feeling better. Hold off on the pellets and veggies, and especially no fruit, sugars, carbs, grains, or starches. Once he's doing really good and he also has normal looking poops, then you could try very gradually reintroducing pellets. Make sure you are using a plain pellet with no added treats or colorful bits in it. And start with really small amounts like 1/4 teaspoon. Then gradually over 2-3 weeks, slowly increase the amounts. By doing this, you are giving his digestion a chance to get used to the new food. If he starts having soft poops or small poops, or acting sick at all, cut back or stop the pellets.
A few things since you're a new rabbit owner, make sure you are using a rabbit safe litter as cat litter can make rabbits sick. And once you do reintroduce pellets and work up to a full amount, you will want to limit pellets to 1/4-1/2 cup per 6 lb body weight, depending on how well he tolerates the pellets. I have a rabbit that I had to feed only hay and veggies to because pellets were making him sick. Your rabbit should always have unlimited grass hay and whenever you do introduce new foods, always do it one food at a time and very small portions at the start, to make sure that it doesn't cause stomach upset. Keeping an eye on the poops is a good way to catch digestive problems early with rabbits. If there are soft poops, small ones, or less or no poops, then it's an indication there is something wrong.
I'm so glad you took this little guy in and that he is in a loving home now
![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
Feel free to post questions you have about rabbit things. There are lots of people on here that will try and help you out.