It sounds like your vet is up on the newer treatments, which is great. I am a tiny bit concerned because "snuffles" is not a technical term and is indicative of old-school vet treatment of rabbits, which wasn't always the best. So the vet knows new treatments, but uses old diagnoses, which is interesting.
I would give him as much pedialyte as he will let you syringe into him--probably no more than 50mL.
I want to strongly recommend a probiotic like Bene-Bac (made for small animals or dogs/cats) or Probios (made for horses). This will help keep his GI tract healthy, and without a healthy GI tract, bunnies can get VERY sick. Bene-Bac is available at most big box pet stores, like PetSmart or Petco, and Probios will be available at a farm supply/feed store, whichever of these stores is closest to you. They have the same ingredients.
Force-feeding him baby food is food. I also would try a slurry of pellets--let them sit in water for 15 min or so, and syringe them to him. Your vet may also have something called Critical Care, which is a powder you can soak in water and syringe feed to him.
Finally, an appetite stimulant and source of calories called Nutri-Cal is often recommended when a bunny won't eat. Make sure you get the malt flavor, as the other flavors I think are liver and fish for dogs and cats. This has a lot of vitamins and calories, and can stimulate appetite. Also available at most big box pet stores.