It seems flow bindings depend a lot on individual binding set up (i.e. strap tension, highback lean, etc) and boot size/shape. I have the Fives SE (without the N.A.S.T.Y.) and I haven't had any problems with shoe-horning. My girlfriend has the Minx, and hers are a little tight sliding her boot in--I think we still need to do some adjusting.
1) With the exception of when my bindings were brand new and having the highbacks pressed towards the ankle strap when my board was in a bag, my highbacks have always stayed down. I now try to leave them open and flat when I can.
2) I can pull up and lock my highback in one motion, while going. Takes a little practice, and will probably depend on if you've got the fit dialed in.
3) I suppose you could strap in on the lift? I've never tried and have never seen the need.
While my experience wasn't with the NX2, I would assume everything would only be easier with N.A.S.T.Y.