Not too sure I understand you question(s) completely. The draw or steadyness?
Your probably using a compound balanced match bow (you must be rich). Not sure what the weight of the draw/string equals, but it should be somewhat easy. You could practice with a regular recurved, or even longbow, bow with a heavier weight pull (40-60lb, etc). This would give more strength/steadness to your compound draw. Or you could go to the gym. Set up a cable pully, at about the same level as your eyesight draw, add a suitable amount of weight and pull back as in your regular drawing style. The stronger you get at the draw/pull the more steady and less tired your hold position becomes, I've been told.
As far as the not feeling or working right in the front of the shoulders is concern, this might be due to you not doing anything in the way of archery for awhile. Too much tightness in the shoulders and not enought flexability affect a lot of BB'ers. The one's who prefer machine workouts, rather than free weights or a mix of both, seem to suffer from this problem. Deep massages can do wonders for any area to relieve tightness. Can also help the nerve paths and the pressure on them.
The traps are a important muscle for holding out and away from the body, as are the delts. Could try those extension exercises like front, laterial and even rear delt raises. Do not work them every day if you plan to do archery seriously, not needed. Good Luck.
