TechWriter,
While I can't offer any better advice than you've already got on repairing this, I'd like to compliment you on how well you documented on your other page how this happened, all the details, etc. And, how you documented how your tow bar is set up correctly, instantly silencing all the folks that tried to suggest this happened due to a faulty setup.
I can see exactly how, why this happened, though, and see it was a case of several factors all conspiring together at the same time and place. It was the one time your toad braking system wasn't functional, and you were on a trip to address that very issue. And, on that trip, you came across those road trenches. And, right when you were hitting them, you were on the brakes hard.
You were probably braking heavily right when rear axles of the motorhome went over one of those trenches you talked about, so back end dropped, briefly making the jeep's hitch point higher than the Motorhome while braking heavy. Heavy braking with no braking on the Jeep, right at the split second that Jeep's hitch point was higher up than Motorhome because of the trench rear axles were hitting, resulted in the Jeep 'jumping' over the tow bar and into your Motorhome. Was a case of a half dozen things all going wrong at the same time, same place, resulting in this. Could've happened to any one of us that flat tows a vehicle, regardless how well we think we have our rigs set up.
Anyway, sounds like you have a good plan on how to fix this. Good luck with it, and thanks for posting back, and giving us more insight on just what happened. Definitely a few things I think we can all learn from this. :)