Good you have him in the 1 gall hospital tank. You can lower the water so it easier for you to change the water and easier for him to swim up for the air.
3-4 pellets 2-3 times a day it way too too much. 2 pellets in the morning and 2 in the evening is more then enough. Sometimes i give them frozen dried blood worms instead of pellets in the morning. A lot of people give them live food which is also good.
Just keep doing 3 tsp/gall of Epsom salt with daily 100% water changes.You can use it for long time longer then 2 weeks so give the forum update. Make sure water the same tempe that he is already in +- 2*. You can pre mix some epsom salt in advance and let it sit. You can use it a few times. Then you can have some pre mix epsom salt that you can prepare 30-40 min bifore (warmer water). This way you can mix it and get the right temp.
Also i am not sure if you know about dropsy. Google it. If he is bloated and swim sideways make sure he is not pine coning. If you look at him from the top see if his scales raised? If you google betta dropsy you will see the picture you will know what i mean.
Good luck, give us update