All that stuff helps, but building a proper offhand position is all about balance, and finding and maintaining a solid natural point of aim. try to center your wobble on the 10 ring, rather than do a "sweep and grab" when you are breaking the shot. that is easiest to understand when you do it with a (high powered scoped. like 15x+) .22 in prone, and you can actually see the pulse wobble sweeping the 10 ring through the scope.
rather than centerfire, try and build your position with smallbore or air. the best target shooters also do a lot of dry fire practice, and use the electronic SCAT or NOPTEL systems to practice with too. then you get in to training regimen, nutrition, avoiding cafiene, and things like that to help manage your pulse rate.
What are you wearing for footwear, or a jacket? That makes a difference too. Highly supported and relatively stiff boots with very flat soles help a bunch.