There are absolutely no plecs suitable for a 2.5 gallon tank.
It is also too small for anything but the betta, the tetras need a much bigger tank, and a bigger group of them.
The best thing you can do is to keep the betta but rehome the tetras. Then feed the betta lightly - uneaten fish food and lots of fish poo will only feed the snails so they multiply faster.
If there are no live plants other than the moss/algae, keep the light on for only a few hours. I assume that you mean algae when you say 'bad moss'. Try scraping it off the tank walls, decor etc. Then with the light on for only a short time, fewer fish and less fish food, it should not grow back as badly - and the snails should stop multiplying as fast.