I have to respectfully disagree with you nsarafov regarding the aquarium salt - I've read many posts on here, and personally been given advice, that aquarium salt should be used only as a treatment and not a regular additive. According to many of the more knowledgeable members on here, aquarium salt should only be used for 10 days max, then give the fish a break for a few days in regular conditioned water, and then try again if the first treatment didn't work.
As for your little guy though GGRiot, I think he looks fine. I would up the water changes a bit though with a tank that small. In the sticky that oldfishlady posted (http://www.bettafish.com/showthread.php?t=115758
), a 1-4 gal tank with a filter, should have a 50% change of water only per week, and a second 50% change with a vacuum to get poop and uneaten food out of the gravel on the bottom. Other than that, it sounds like you're doing a good job :)