Bit of advice-
Get the PVP sword, dump your dagger. It's not really worth losing all the extra damage from a sword just to be able to use ambush/backstab, you'll be hurting your opponent much more with swords
Scrap sub spec, you want to be killing your opponent fast, and getting some nice damage in. Go for something like this (Once you get the PVP sword):
WorldofWarcraft.com -> Info -> Classes -> Rogue -> Talent Calculator
If you're sure you're going to keep him as a 49 twink for a long time, throw Mongoose on the PVP sword, put it in your main hand and keep your current sword in the off hand with it's current enchant. Crusader would work too since it's pretty cheap and has a good effect.
You don't have to take my advice, just some tips
