I understand your frustration. RV Quality Control is non-existent....Dealership has no interest in you after a sale. All around PITA.
One question........you made a comment that I found confusing
"I checked the air pressure on every fuel stop"
When checking at every fuel stop where you adding/removing air due to different tire pressure(s).
Tire pressures should be check & adjusted when 'cold' (not driven on for several hours and at ambient air temp)not after running down the roads at speed.
By doing so you may have contributed to your tire blow out....tire was actually 'under inflated'.
Towmax is not the only tire mfg. that wants the old carcass for inspection on a warranty claim.......Goodyear has same procedure (as I sure many mfg. do).
Goodyear schedules pick up/pays for shipping. FedX guy picked up tire next day AT tire dealer.
You are correct.........mostly you are on your own