OK qA teaspoon for 5 gall ,which is 1 tsp/gall? Am i right? it's not a therapeutic dose at all. I think you follow the box instructions? The box instructions just for preventative care. May be that why it not helping at all.
I know that you treating him for about 7 days but How long you have him?
Is your tank filtered?
How much and how often you usually change his 5 gall tank water?
Is he still acting healthy(eating and active) which you wrote yesterday that he is. How he is acting today? Is he acting the same or worse?
The right dosage for the aquarium salt is 1tsp/gall up to 3 tsp/gall with daily water changes.
If your tank is not cycled i would start him on 3tsp/gall of aq salt. You need to do full water changes daily. You can lower the water so it will be easier for you to do water changes. Do not keep him in very warm temperature. 80* is too warm. The warmer is the temp - more chance for the infections. So if you can 76 * is good.
Sress coat is also good for healing so i would continue.
If his behavior changed i would go with API Triple sulfa .
Do you know how to acclimate betta to the new water if you need to do full water change?
If your tank is cycled then it would be a little different. Let me know if your tank is cycled so i can give you instructions.
I also thinking he might bite them too. Of course fins can get infected from biting too. So i am not sure what he has but if he is acting healthy i am really recommending to do full dose of the aq salt treatment. And buy the medications so you have them on hold(API Triple Sulfa).
Some of his fins are healing if it clear, transparent regrowth .