You should receive fair value for your car. The insurance company cannot be forced to pay more just because you demand they do so. As you state, it is only $500.
You should remove references to your military service, you are playing emotional blackmail. You infer the stress caused by this incident endangers you and your troop. That is not cool. You should let someone at home handle this if it causes you so much trauma.
I thank you for your service and will pray for your safety.