1) Sandstorm will work great, although rocks are helpful, they're not required. Gliscor's not the only rock setter out there, you can just have another =)
2) Sand veil will work fine to help his evasiveness. Besides, if you don't have Sandstorm, as you say, there would be almost no point in having Sand Veil.
3) If he's a wall, then yes, it's fine to use Sandstorm as it blocks Lefties and hinders your opponent besides. Just make sure it doesn't hinder your teammates!!!