For lapping stones I use a DMT 325 (it's a diamond covered plate). Sometimes I'll notice a scratch I missed on the stone and it is usually about 1/4 of a hair thickness. So it is very shallow. You can pick up a diamond plate at most home improvement stores for around $10. It might not last as long as a DMT, but then again, it might last you a lifetime.

For me, light honing pressure is the weight of my thumb. I put a 3/4" block under the hone and stand so my left thumb can lay across the blade and my left hand can follow it. The extra block keeps my left hand from cramping.
Heavy pressure is my thumb pressing down with maybe half a pound of force.
Unfortunately, a whole lot of the pressure thing has to be learned by feel and sound. When the bevel is set, the blade will smoothly go across the hone with even vibration and the sound will be consistent.