Yep, going through a specialty insurer is about the only way to to make this work. Just be sure there are not any mileage limitations, some specialty insurers also require the car to be garaged.

My internet connection is too slow for G drive to work.

If the car is as bent as described another shell may be a better route.

If you are going to fix, there also comes a point where " clipping " the car is less work / better result than rebuilding floors / rear panels. ( RE getting a bunch of loose parts to fit together is more difficult than installing a prewelded chunk. )

The car would be cut across the rear pillars ( between the rear door and rear window. ) and a zig zag pattern across the rear floor / rockers. This zig zag pattern would be cutting the car apart where the factory seams are not an actual ZZ across a flat surface. If a factory seam can't be located an overlap weld is a must.

Clipping a car is a fair amount of work but not impossible to do with good results, you just need to decide if you really want this particular car to go again.