It wasn't clear to me who was at fault until you posted this... He should absolutely refuse the other insurance companies offer, do the above on the comparables, go rent a car (I'll assume his policy has rental coverage) to tide him over and advise he'll send them the bill until they come back with an equitable offer to replace. Do not fully settle the claim until any and all possible medical expenses are cleared within the the first 10 months or so, as to fully settle, he is entitled to a "pain and suffering" payment to fully close the claim. It is very negotiable.

Charlie