So it's not the bumper that broke, it's the bolts that stripped out? What did the threads on the bolts look like? I have not seen the horns on the Xterra, but there are many ways to fix the holes without needing to weld. The sad part is it sounds like the bumper is now deformed. I hope it matches back up.

Just curious, what were the bolts torqued to? I don't know if Shrock has suggested torque specs, but I would treat it like a tow hitch (since it is a recovery point) and torque them down to no less than 70ft. lbs. or so.

Also, when you were being pulled off the trail (or any past recoveries using the bumper) were you being jerked? If the bolts were not tight the extra jerking could have weakened the threads.