Hi ya Greystone,
I have played a pixie solo game so I may be able to answer a few of your questions.
Firstly I found that the kung fu damage that my pixie delt out was comprable to that of other races.
Secondly the weight that a pixie will be able to carry when he/she has full strengh will be very low, my pixie was able to top out at only 90lbs, so you might want to consider the kung fu option because some of the better swords take up a fair chunck of your 90lbs.
If I remember rightly my pixie could do around 50 damage with hes kung fu so that does compare well with the better swords, I would recomend that if you go the kung fu way that you also teach him some sheild skills as holding something in hes 2nd weapon slot will enable him to kick as well as punch making better use of hes kung fu.
As far as breaking open chests I found no difference from other races.
You might want to consider starting as a wizard instead of warrior, the reason I say this is because I find "Merlins Sheild" very usefull in the first half of the game. It can be used to protect you from the traps in chests and will give you a good amount of protection from vomit(zombies), swamp muck and mantraps.
My ideal role accension for a pixie would be:-
Wizard(lvl 14) -> Barbarian -> Samuria -> Paladin -> Ranger -> Assassin -> topping out as Zenmaster or Valk.
I hope this helps good luck and keep posting as to how your game is going and what choices you finaly make.
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......shake it baby.