No problem. I actual meant to say Maracyn II (sorry I am treating my other fish with Tetracycline--Maracyn is best for Dropsy). Ok, continue the Maracyn II. In fact, if you can, it is even better to combine it with Maracyn I. Make sure you do the 100% daily water changes and epsom treatment.
Sorry, I should rephrase that, don't do salt baths. You need to treat him with salt and leave it in his tank. You can't do salt treatments for more than 10 days. Just add 1 tsp/gal epsom salt to his aquarium and do 100% daily water changes where you replace 100% of the salt each time you do a water change. Same goes for the Maracyn, make sure you replace the medicine after each water change.
84* is perfect.
You really need to get him to eat something. Have you tried frozen blood worms? Daphnia are good for constipated bettas, but frozen blood worms are bright red and great for stimulating eating. If you can get him to eat something, then you can soak his food in metro and feed him that. You can get pure metronidazole from your local Vet for cheap. Just explain the problem and they will probably be willing to sell you 1 or 2 metronidazole capsules. I've done that before.