The torso length could be part of the issue. If you don't know yours go find someone to measure you. I believe it is fromt the base of your neck to the waist but someone who remembers better than I can calrify.
Also, as far as the pack goes, there are a few things you could do. I've never actually taken a good look at the pack so I don't know what kind of adjustments it has but I'll take some shots here.
1. Your waist belt may need to be tightened a little more. Make sure it is around the belly button area(at least that is what I do) so that it rests on your hips and doesn't just end up being their for decoration. This'll take weight off of your shoulders and collarbone. I know on the waist belt for my pack, there are straps to pull t closer to the bottom of my back to help as well.
2. As far as the shoulder straps go, those adjustments are of course dependant upon the individual. For me, when I go to put me pack on, I lean forward so my torso is at or near a 90 degree angle and my pack is resting on the top of my back,then I pull the straps to tighten the pack to me shoulders. Not too hard otherwise they'll be too tight and you'll be losing circulation.
Then I put on the wist belt and adjust that properly. Then there are other adjustments just above the shoulder straps right over each of my shoulders that I pull to pull the pack closer to my back. After that I'm usually good to go.
It may be one of those thing you really have to play around with. Oh, and while I remember, you don't want to pull the strap that goes across your chest very tight. That'll make things uncomfortable as well. That strap is simply just there to keep straps from sliding off of your shoulder and that's it really.
Hope this helps.
In all things of nature there is something of the marvelous.-Aristotle