Glad to hear he is doing better =)
Be careful with the salt, unless you are treating him for an external illness, it's recommended not to use it on a normal basis. You will have to do another 100% water change next time, or 50% without salt for a few changes to rid of it without over dosing him. In the long run it can cause the parasites and such to become resistant to the salt and treatment won't be as effective when it is truly needed. Some believe it can do long term harm to the bettas, as some are sensitive to the salt.
If you continue with the salt, you will have to up the water changes (which isn't really good to over clean the tank) to 100% each time. Just make sure you dissolve the salt very well prior to adding it with the fish. If there is even one grain, he can find it and it will burn him.
I'm sorry, salt is fine to use short term for a preventative and to heal certain ailments, but I'm personally against using it unless it is needed.
May I ask the size of the tank, since 2 water changes in 2 weeks is a low amount, want to prevent something similar happening again.