Car was total loss after mechanics test drive?

Simple fix on my aftermarket 2016 Subaru WRX STI limited. Debris in the road from a separate and non-involved accident damaged my tires. Changed a flat to the Donut and had it towed to a close tire center through insurance claim. The engine was running great before leaving my house and the day of the accident claim. I heard it was discovered that something either moved or loosened my steering column. Car gets moved to another location for that repair because main place only does fluids and tires. Tires and steering column; both don’t really require getting into my engine or aftermarket parts. A month has passed. I’ve called pretty much every couple days to ask what’s going on with repairs with not a lot of update. A couple days ago I get texts about starting the process for a total loss claim and enter a panic attack. I call everyone; insurance, autoshop, and adjuster. I’m not getting straight answers as to where my car is or what happened besides “it was leaving the lot and then just died” a lot of “it could be anything, hole in your oil pan, bent piston or valve”. Push comes shove so I call the manager of the main location and press on who to call or where the car is; doesn’t tell me besides saying it’s a sister location in another city no number or address. That’s fine I found it on google. Press on when I can go see it and get answers about later because it was the afternoon and probably didn’t want to deal with it. I then say I’m going today (2 days ago), in the next few minutes. Get the sound of panic and leave. Arrive. Guy brings me to my car and turns my car over to the sound of something bizarre and unfamiliar. Ask him out and open my hood. Nothings hooked up; bare wheels where belts should be lined up, hoses cut. “Yeah my guys were really digging in like bulldogs trying to diagnose why it’s got low compression but insurance just told us to stop and it’s a total loss” okay. See my c.o.b.b. disconnected from the steering area; start checking codes and my tune. Overhear an employee walk up and speak to manager “oh yeah that computer gave me a bunch of bullshit” or something similar.

Check my tune and see it’s been reflashed to something unfamiliar and try to reset the ECU and see the battery has been drained probably from them starting over and over. Check oil and it’s darker than the brown I was used to and about 80% full. It isn’t starting for long and the rpm is way too low and shows way too high of a pressure for my turbo and boost. Get the ecu reflashed to my tune meant for the parts I have and it starts to sound way better. Give up because the fans and all the tubes detached make me worry about overheating. This car is my baby; it’s rebuilt and has really low mileage for the year so idk why something like this would be happening in the area they say it is. My insurance understandably isn’t going to pay for a entirely new engine without totaling my vehicle. What should I professionally do the be sure my car gets properly repaired without being made to pay for damage that wasn’t present at the time of my claim or accident (they didn’t let me argue my case until I actually went through my security camera feed to show my car running and driving perfectly few minutes prior to leaving on the tow truck)

Any and all advice would be greatly appreciated!! Thank you.