In a second career, I flew as a courier on a number of C-5 missions. I suspect that the Loadmaster was riding with the crew on the upper deck unless he/she was performing a last minute inspection of the cargo deck or checking for fire in the aft troop compartment area.
It looks like the fuselage separated near the crew lounge/bedroom area.. The courier seating area just forward of the wing box appears to be in pretty good shape and it looks as if the emergency egress slide is deployed from that area.
In looking at the close ups of the broken section of the fuselage forward of and still attached to the wings, I have to agree. The squared off piece of equipment on the right side (left side in picture) that looks like it has a bite taken out of it looks like it might be the forward end of the crew galley.