is the cure poison potion (and fountains, altars) the only ways to cure poison?? cuz im running out of the potions in the temple. is there any kind of magic spells that dispells poison? also, does it wear out after a while, like the other spells?

Restore health will cure poison. Cure poison will cure poison. Spider nectar will cure poison (but you want to keep at least one of those for the ritual to get even further into the Serpent Temple).
Don't recall is poison ever finally wears off. If it does, it takes so long to do so that you don't want to risk your character dying and cure them one way or another.
Obviously it is a good idea to stock up on cure poison potions before entering the temple.
Wyv

The yellow flasks hold the cure for poison.

Cheers,

Don't waste your potions trying to cure poison after every fight. The poison only causes minor hit point loss over time and you will keep getting poisoned by just about every creature in the temple. You couldn't possibly have enough potions. Use healing potions and spells to counter the poison until you have cleaned out most of the nasties, then use cure poison at the end. My party was poisoned pretty much the entire time in the temple.

You could turn your spawning frequency to low for a while too.

Good hunting.