My experience with insurance companies is to keep pushing them they will always offer up the lowest value and know that some people who are experienced will push for a more appropriate price and most companies will pay up if you push them. It helps if you can show recent work and prove that the condition of the vehicle was really good vs say marginal etc. If you had any costly modifications added make sure you share those like say the wiring for the camper, maybe airbags to support the camper etc given that does impact the vehicles replacement value and should impact the insurance companies view of its value.
Cracked frames in most states are instantly put on scrap status and you cannot fix them. So your dead on saying no way!!! And pushing to have it totaled.
By the way my experience with insurance companies is that only a couple of them ever actually do their jobs well. I have nothing but good things to stay about State Farm and would not want to be found at fault have a different insurance company and be facing a State Farm covered person. My dad was in a bad accident years ago State Farm even sent an Agent to his house to drive him to a doctors appointment, had a replacement rental in his driveway the next day after the accident and paid for all his lost work time, child care costs etc. Then when the offending driver filed a lawsuit against my dad State Farm sent three lawyers to the court with past history which apparently this driver had done this two years earlier hit a family then sued them etc. State Farm lawyers had the case tossed the judge yanked the persons drivers license then State Farm sued the owner of the vehicle the person had borrowed and was driving uninsured to recover the $150,000 in medical bills and lost wages my dad suffered and was paid out by his own State Farm insurance. Last we heard the owner of the car was forced to sell his house to cover the cost of the accident.
My dad spent 4 weeks in the hospital major injuries and over a year in rehab. Head on accident with a Ford Explorer doing an estimated 65mph in a 35mph zone which lost control crossed over and hit my dad head on in a 2001 Honda Accord. Ugly accident both cars cleared a 15ft wide 12ft deep irrigation ditch and were upside down in a field.