New Playthrough K/T

Hi guys i'm trying to complete the hole trilogy with a new character this time around i wanted to play Kensai -> Thief for Kai and Grandmaster
So what i really want out of this character is a good backstabber and just all around good fighter
I want my endgame weapons to be MH: Dagger of the Star +5 to restealth and backstab again
Off: Short Sword of Mask +5 to root target + level drain
another weapon choice is MH: Angurvadal +5 higher backstab dmg + 22 strength
Off: Dagger of the Star +5 restealth and backstab
or Mh: Dagger of the Star +5 restealth and backstab
Off: The Answerer +4 -15% magic resist each hit
It should look like this cast improved haste on me than send my group in and i come for the backstab and my damgae should be pretty good without stealth but because of the dagger and improved haste i should be backstabbing like most of the times or thats how i immagine this character
So my problem now is how the hell do i spend my proficiency points i thought of going two weapon style and Dagger in BG1 for Dagger of Venom the Problem is if i go with dagger there are no good ones in BG2 until Dagger of the Star
Ok my question now is should i start with Long swords than go daggers ?
Another Option is going Multiclass for fighter HLA with improved haste and Crit ahhhh i dont know what to do pls help me!!!
ps: if i go dual class than i dual my kensai at lvl 9 so i dont have so much downtime
So what i really want out of this character is a good backstabber and just all around good fighter
I want my endgame weapons to be MH: Dagger of the Star +5 to restealth and backstab again
Off: Short Sword of Mask +5 to root target + level drain
another weapon choice is MH: Angurvadal +5 higher backstab dmg + 22 strength
Off: Dagger of the Star +5 restealth and backstab
or Mh: Dagger of the Star +5 restealth and backstab
Off: The Answerer +4 -15% magic resist each hit
It should look like this cast improved haste on me than send my group in and i come for the backstab and my damgae should be pretty good without stealth but because of the dagger and improved haste i should be backstabbing like most of the times or thats how i immagine this character

So my problem now is how the hell do i spend my proficiency points i thought of going two weapon style and Dagger in BG1 for Dagger of Venom the Problem is if i go with dagger there are no good ones in BG2 until Dagger of the Star
Ok my question now is should i start with Long swords than go daggers ?
Another Option is going Multiclass for fighter HLA with improved haste and Crit ahhhh i dont know what to do pls help me!!!

ps: if i go dual class than i dual my kensai at lvl 9 so i dont have so much downtime
1
Comments
Also, you don't have to worry about downtime as much when you're dualing into a thief, they share the fastest leveling rate in the game with bards.
As for a Fighter/Thief multiclass, well on one hand, it'll be more survivable than the Kensei - Thief, as they can wear armor, but on the other hand, they'll only be able to put two pips into a weapon, which, admittedly, does allow them to wield a larger selection of weapons more competently than a five-pip focused fighter. If you want a full on devastating backstabber, you want Kensei - Thief.
Because in Tob there are a lot of enemys backstab immune and with dual weapon style i would have more dmg right?
I'll admit to some personal bias for Single Weapon, though. I just love the idea of it. Dual-wielding or great-weapon wielding gets a little boring after a while to me.