i would keep him in the hospital tank until you sure he is recovered. Don't need to use filter when you treating especially if you adding medications. I don't know anything about silver solution. I never saw anyone recommended it.
Be really careful with bettafix i read that it can kill the fish if you overdose. A lot of people on the forum don't recommend to use it. Especially if it contain aloe don't use it. Not sure about ingredients.
If he don't have any visual symptoms on the body, his behavior back to normal (active like he was before and not laying on the bottom or just hanging on the top), he is eating. I would just keep him in the hospital tank and do 50% daily water changes for a few days and see how he doing before you put him back in his tank .
I would also quarantine live plants. And silk plants i would disinfect before you put it back with him. But just hot water is not enough though. I can give you instructions on disinfection tank and silk plants.
Also even though you do 50% and 75% you still need siphon the gravel in the tank regularly:)
I hope he doing good.
I would rally recommend to stop using bettafix...not sure about other medications. I always research a lot before i use anything from the store. There is some medications that people recommended because they had experience with that. Don't believe what you read on the bottles , be careful.
I didn't know that you can use filtered water without water conditioner. I though you still need water conditioner. But i guess you know better since you are using it for your betta.
I would have aquarium salt on hands in case you need it.