If he is in one gall up to 2 gall you don't need a filter. Just do not use filter for that size. You don't need to cycle small tanks. You can do 50% and 100% water changes a week. I tried to go through the pages how i understand you have him in about one gall tank? If the reason he was not active is because of the filter then he should be back to normal pretty fast ufter you take the filter out. If not then something is wrong. Did he behave differently when you just bought him ? A lot of the time betta can be sick. And of course it not your fault it probably happened to everyone on this forum.
Is he eating? Did he ever eat?
Also i want to tell you i read so many post on this forum and there is a lot of people who even had bettas in the row died and still go for another betta and finally get healthy one. It always a chance to buy sick betta especially if you not experienced.
Also give us update so we can decide if he is really sick and you might need to use salt. A lot of time salt really helps. Salts have antibacterial/fungal affect and improve their electrolytes level.
Also did you ever check your water. When you go to the store they can do it for free. Next time when you go check the water just to rule out the water problem which a lot of people have. Some people have ammonia in the water, then its advised to use Prim water conditioner.
I would really advice to have salt on hand so you can use it in case we will decide he is sick. If he is living but if you took the filter out long time ago and he still hanging on the top and not moving and not eating i would assume something is wrong.