I was wondering about dual wielding and just thought to ask, when you PRESS both attack buttons and you have a sword in both hands and you do that light dual slice thing-and you are sneaking-do you do DOUBLE the amount of sneak attack damage you would with one blade? Like if i had the backstab perk which allows for 6x damage and I had two swords would that come out to 12x damage? What about if critical hits were thrown into the picture? How much extra damage does a critical hit account for anyway?

I'd assume that you're doing twice the damage, but you'd still only get the single multiplier. So you'd have the 6x damage,but it would six times the damage of the two swords combined.
Although I know wih daggers, a dual-wielding power attack with both weapons results in a sort of flurry of dagger strikes, but the two blades never seem to hit the target at the same time. Maybe it's the same with swords?

No no not that power attack, you can PRESS both buttons and do a twin swipe of the swords or whatever your weapons are. The attack does not consume stamina. Its not the flurry of movements power attack.

I think the answer to that is a yes in my experience. Dual sneak hit is helpful for leveling up sneak twice as fast. When both blades hit, you get credit sneak experience for both hits. And in early level, your sneak experience can go up two levels with one successful dual hit attack.

It's not really 12x damage. It's more of 2 separate 6x sword damage that adds up to 12.