You can collect money from the insurance for the total value of the car. But if you tell them you want to keep the totaled car, they deduct some amount (because they would sell it to a salvage yard and now they can't do that). Then you can take it somewhere and have it fixed or fix it yourself or whatever.
You end up with a salvaged title instead of a clean title. This would make it harder to sell the vehicle but that didn't matter to me as like you I wanted to keep it and run it in to the ground.
A factor I was not aware of is that your insurance rates for operating a car with a salvaged title will be higher compared to having a clean title. (I'm not even talking about full coverage which you couldn't get any more, this is for liability only — you pay higher.)

My brother is an insurance agent and helped me evaluate things. It ended up not being worth it to keep the car, and I bought another similar aged vehicle. It's a pain finding another used car, but it was a better financial decision and I like the car I got.

Also FYI - I was able to get just a little more out of the insurance company when I informed them that I had just put on new tires on the totaled car. I had to show them the receipt.