I couldn't see the pictures. I hope everything works out for you. Here is my unsolicited and non-professional advice:
-Talk to their insurance company. They should tell you pretty clearly if they accept liability or not once they finish their 'investigation'.
-Keep everything medical, they have to cover all of those charges once they accept liability. They covered my evaluation and muscle relaxer pills. I needed nothing more, it was like $200. Your situation will obviously be more in-depth and I don't know how all of the medical will work.
-Back injuries can show themselves many, many days later. Sometimes it takes twisting/turning the right way to display symptoms. MAKE SURE YOU ARE GOOD before signing away your medical rights. This process can take weeks, don't be in a rush.
-You have the right to take your vehicle anywhere to get evaluated.
-Take it to 2 or 3 different shops. IMO avoid where the insurance company tells you to go. They have a deal with those shops to charge less and you'll end up with lower estimates.
-Submit the highest estimate to the insurance company. If the shop is reasonable in their assessments and costs, the insurance company will accept. They will mail you a check for the full value of the repair assessment.
-Go to a dealership to see what they will give you for the trade in of the damaged truck. The trade in plus insurance check might be worth more than the truck.
-If not trading in, take your truck to any shop you want. I'm fairly confident you are not required to have the vehicle repaired at the shop you submitted the estimate for. If the repairs come out higher, submit the additional charges to the insurance company. They understand that additional damage is sometimes found after body panels are removed. If the repairs come out cheaper, keep the excess money.
-Make sure your truck is fixed before signing off as repaired. If something is messed up, make the shop fix it. This includes new paint blemishes/orange peel.
-Sometime in this endeavor, have a discussion with their insurance company about the diminished value of your truck. They can increase your payout because their customer cost you money. Insurance companies are required to restore you to your previous condition before their customer hit you.