I would recommend setting up a Virtual Outfitting appointment here. This way we can make new recommendations and discuss fit. A Virtual Outfitter can narrow down a couple of options, and then you can always go try those options on instore. A advantage of going into the store is the ability for REI green vests to swap out shoulder straps and hip belts to adapt to your body. It sounds like you may need a medium size frame but smaller shoulder straps to adapt to your smaller torso. The Osprey Aether and Gregory Baltoro are two options that have these adjustable parts. 

Hope this helps!