It is very important to understand that sole thickness must be maintained when setting a shoe back under the foot. The excess foot that overhangs th shoe must NOT be thinned back through the wall, but rather just beveled on the bottom edge to continue the rolled toe effectfrom the shoe edge. If there is enough sole depth and the shoe is placed correctly this rockering of the bottom edge of the foot will not invade any sensitive tissue. As for the coffin bone question, if the calks are raising the foot up, but there is no support under the frog, then I recommend adding some type of plate, hard pad, to get support under it. It is the internal tissues you need to concentrate on.
Calks have another disadvantage as an 'angle raising' device.
They sink into soft ground and are are then immediately ineffective. Their only correct use should be for traction. I use a full wedge pad with frog support on the bottom side, or a hard bar wedge pad instead, because it holds the foot up to the correct angle even in softer ground. Just some sugestions. Since he has the caulk shoes on, the coffin bones appear to be at an angle to the ground, but if I look at the top of the shoe and the coffin bone, they are parallel.