proper weighting can definately fix alot of that....you need more weighting on top of the shoulder to upper arm joint....and less of the side of the torso weighted to the upper arm

-also, the clavical bone is going too far out (as in too long), it should be shortened to the point where the top of the upper arm joint is at the very start of the shoulder...not halfway throught it

- once these adjusments are made...if you need even more control...you'll need to use influence objects