Oh and I should mention, while this type of character is VERY strong against most enemies..... You will have a tough time with most dragons.
Summon two storm atronarchs and things should change a bit, as long as the dragon doesn't go for you hehe.
Maximize BS damage:
Level up one-handed, take the basic perk that increases damage.
Join the dark brotherhood. That way, your backstab will do double damage if you wear the gloves you gain from it.
Improve smithing to be able to upgrade your dagger to legendary, this way you'll once again do double damage compared to if you wouldn't spend time increasing smithing.
And of course the sneak perks. Assassin's blade for a base x15 for daggers.
The game is super easy once you one-hit kill everything with sneak attack. (the things that can't be sneaked on will be a problem, but anything that can't be sneaked upon can be killed with double summoned storm atronarches (or frost atronarches) and then running and hiding again and see if your atronarches kill the enemy. If they don't, try a new backstab. I'd put some points into destruction though, if you plan to fight dragons. If you don't, you don't have anything to worry about.