Sure glad your unmarked by the hand grenade but I'm afraid anything else I can say wont comfort you much.
That frame is toast for all intensive purposes. When that top strap stretches', everything else that needs to line up shifts position as well. The bore and axle C/L will never return to original orientation without very stringent metal jigs to help with line-up. I'm not saying it is impossible but unless you have a buddy with some very expensive measuring equipment that only the most proficient miachinist/tool maker could use and will do the work free, a commercial program cost would be many time the gun's value. Even if you can get it trued up again , I would be suspicious of cracking started at the corners & junctions of the frame pieces from the original injury and maybe compounded during straightening.
A month ago you could have ordered a new frame from VTI but unfortunately that window was slammed shut.
As far as cause of the original injury goes we probably will never know if it was a double charge or the fact that the fickle fait of Italian gun manufacture just jumped up at you... I am forever getting jacked up on this forum for saying that even though they are chambered for magnum or similar rounds....they just aint strong enough sometimes and their aint no second chance on a hand grenade...when those BP designs get hit with a Smokeless powder pressure curve 1873 designs loose every time.
