My Typhlosion Had the pokerus but it has been cured. Does he still get double evs from pokemon or does he only get to keep the double evs he got with the pokerus?
Yes, the effects of Pokerus linger, even after the Pokemon is cured. Being cured of Pokerus simply means that the virus can no longer be spread by/to that Pokemon.
Yes, but Pokerus can't spread after it's cured.