I've been preoccupied off-site lately, and haven't gotten on much. Lots to catch up on.
My observations- we've rented uhauls. The $8/day sounds like safety on the trailer. A test reservations shows this as the rates around here:
Now, their FAQ as to when damages must be paid if not covered by a damage waiver also says this:
Not going to opine whether their failure to charge upon return absolved you of responsibility, BUT, an argument can be made that company policy appears to require charging upon return, and, how can they prove damage charges now being made aren't including damage that occurred somehow AFTER the return?
As for stonewalling or obstructing insurance info... didn't the police ask for it at the accident scene?
Also, I'd wonder what your personal exposure becomes if your blocking answering causes some deadline to pass voiding some subrogation notice right uhaul or the other vehicle owner would've had. There may be some state law regarding your compliance. There could also be tons of fine print in the boilerplate sections of the rental agreement.
End of the day, you rented a piece of equipment. You chose to drive in the weather that was happening. You hit something and did damage. If the truck had defective suspension you could've swapped it out for another unit - we've done that many times with uhaul and penske both, everything from rough idle and engine lights on to just having cupped tires that rode horrible. If you had a valid damage waiver you call and tell your insurance that. Then you turn over the info anyways, and let your insurance assert those defenses because you know they won't want to pay.
That's my thought anyways.