i find myself having my shoulders more squared toward downhill, and i assume that is what you mean by being opened up. it seems unnatural to not have my shoulders pointed to the direction i'm heading to, but i will try to have my shoulders being parallel to the board and only have my leader shoulder be the steer rather than both my shoulders at a slant.
i'm still a little bit confused at the bend, during a heel side my butt should be doing a barbell squat or sitting type motion, while in a toe side it's a pelvic thrust right with a small bow or arch of my back?
For shoulders, think of your snowboard being the bottom of a cereal box you generally want to keep your body parts inside of the box...even when you tilt the board/cereal box on edge...your body will also be leaning. As for pelvic thrust..."small bow or arch of my back?" is too high of center of gravity and on the backside of your body, you want the hump on the frontside. For humping...pelvic thrust also involves a pelvic tilt; isolate these muscles and do them at the same time...sink in your knees, tighten your butt cheeks and tighten you lower abs...your pelvis should then hump....got it...now stand up from the computer and give it a try.