Had the same subframe and luggage rack problems when I used hard luggage of road.
Once I switched to soft luggage that was the last problems I had.
For of road soft luggage absorbs a lot of the vibrations and impacts.
Getting hit by Cars is hard on any set up glad you are OK.
It was hard for me to do the switch also (Dry safe lockable hard cases are nice) but once I cracked open one of my BMW boxes on a rock it was easier to do the switch.
I am looking at a grate basin Giant loop bag for the next Adventure. My old Gear is getting long in the tooth.
All the best for the Journey .