Re #5 you can use the departure MDR that says v/s = GS * climb gradient.
12*540 = 6480 ft/min.
This rule works when using the units of climb gradients (as well as descent gradients), knots and feet/min ONLY.
This MDR rule is normally used for departure (because SIDs have 'climb gradients' wheras glide slopes are in degrees), but since the angle is the same whether you climb or descent, it can be used here, because it is a gradient.