Hey colwest, my suggestion was mentioned for everyone.
In your situation, I wouldn't spent more money either until we have a perfectly working solution. Maybe you can contact the support and get some kind of refund? You are definitly not the first person with this problem.
As far as
@VLud found out, the only solution is to make a backup of the memory chip with a hardware programmer. Unfortunatly it's not possible to copy another backup to the memory chip. It must be the orginal one.
The idea of these adapters is nice, but the way of working seems a little suspicious to me with their "fakeiOSDevice" which connects to the headunit like a middleman. I think that is one reason why Apple didn't provide an offical solution.
Hopefully you didn't feel offended by my reply.
Best Regards.