Need better pics to give you much, and I'd strongly advise your friend getting rads. *Make sure the vet marks the hooves for the xrays - dorsal wall, point of frog & hairline.
Yes, by the sound & look of it, you may not be able to do much immediately, but you do need to get those heels significantly lower, just not in one fell swoop. I would be, as you suggested, taking the heels back on an angle *to the current ground plane* so that the bearing surface is (more)correct for the bony column, then I'd be lowering them as much as possible, but without drastic sudden changes - eg. generally no more than *up to* about 1/2" a time, but you could trim weekly for a few goes, to get the bony column quickly aligned. Weak heels will also have a bearing on how low heels may be able to come down, but sounds like the horse needs padding/soft footing anyway.
I imagine, esp if the horse has nearly penetrated, it will indeed be painful to stand on concrete or such, let alone putting extra weight on one while you hold the other. I'd be keeping him on soft, yielding footing, &/or protecting wherever necessary. For the sake of pics, you can stay in the soft stuff, but get him to put a hoof on a piece of ply or such, to take on the ground pics. If he must be taken onto hard footing, or he's sore even on yielding, soft ground, ensure he's got thick enough foam rubber/styrene under his feet(poss with a crescent cut out for now to relieve tip of P3 if penetrating).