With a buried lie you must use your sand wedge as a digger to get below the bottom of the ball so square the clubface to dig into the sand and create a more downward swing arc
Stop thinking about how far back to take the putter or how hard to swing, your mind can do that automatically, and you can prove this by practicing your long putts by just looking at the hole and stroking the putt without looking down at the ball
Reverse pivot means that your pivot is going in the reverse direction that you want it to, when you turn back to the right your weight should follow you and the same applies to the through swing, this is usally the result of a poorly balanced set up