EVs work differently at Level 5. Different amounts are needed to get the desired stat. Going with a standard 4/252/252 and such will only end up with you wasting EVs.
Snover's moveset is fine, but I would give it the Eviolite over Oran Berry. Also, its EVs need changed.
Snover (M) @ Eviolite
Trait: Snow Warning
EVs: 196 HP / 196 Def / 116 SDef
Bold Nature (+Def, -Atk)
- Blizzard
- Giga Drain
- Leech Seed
- Substitute
For Vanillite a 68 HP, 196 Attack, and 236 Special Atack EV spread with a Brave Nature will serve you best. Then give it Hidden Power Rock, which is one of the few Hidden Powers which won't lower any of your important stats in this case.
Take out one of the Cubchoos before you get incredibly swept by a Timburr or Croagunk among other things. And then give the surviving one an EV set of 116 Defense, 196 in Attack or Defense, and 196 in Speed. And if you choose the one with HP Water, give it Surf like you did the one above it.
Then with the space left by the last guy let's put in something non-Ice type. A Solosis would be good, seeing as it isn't damaged by Hail.
Solosis (M) @ Eviolite
Trait: Magic Guard
EVs: 156 HP / 36 Def / 240 SAtk / 36 SDef
Modest Nature (+SAtk, -Atk)
- Psychic
- Calm Mind
- Recover
- Hidden Power [Ground]
Instead of Clamperl, how about Frillish? It can give you the help you need against Fighting types, in addition to the Steel resistance already given by being a Water type. You can still keep Clamperl over Frillish if you want though, because Clamperl does sweep well. However, just beware of Mach Punch, Vacuum wave, and Bullet Punch for your team.
Frillish (M) @ Eviolite
Trait: Cursed Body
EVs: 236 HP / 36 Def / 236 SAtk
Modest Nature (+SAtk, -Atk)
- Blizzard
- Scald
- Shadow Ball
- Recover
Finally, let's not have DynamicPunch, okay?
Timburr (M) @ Flame Orb
Trait: Guts
EVs: 76 HP / 196 Atk / 236 Def
Adamant Nature (+Atk, -SAtk)
- Mach Punch
- Drain Punch
- Protect
- Payback