EVs: I don't know either becase I don't know how they work, but I would just train him normally, like leveling up.
Ability: Thick fat (if you want, if you are able to get one from the dream world in gen 5)
Snow Cloak (oblivious won't be very useful since there aren't many Pokemon that will use attract on you. There are more that will make Hail so you're evasion will be raised.)
If I were you I would remove Blizzard since it's a special and his special is the worst and give him avalanche since it's a psyhical move.
Also about that missing move I would give him ice fang.
Just go to a move tutor with a heart scale (you can get them from the pokeathlon exchange corner or by smashing rocks) and go to the move tutor in Blackthorn City and teach him ice fang.
Also I don't recommend Hail, go with Ice Shard.
just to recap:
ability: Thick fat (for gen 5)
Snow Cloak (for any others)
Hope this helps :)