I just went through a 6 month version of the same thing, what you are way ahead on (from me) is buy back, I could only pocket $1900 if I wanted to keep my car (which was way up from before negotiating similar crap as you). They hauled it off and I'm piecing a swap together now. That said, I should have just kept my car, nit picky stuff adds up. That said my car had lots and lots of goodies that went away with the car, so every situation deserves different paths.
Lessons I learned.
1) when in a hit and run chase down the offender until they stop.
2) if you hit someone in my area run, the fine is $400 if you admit, if you don't admit you will not be liable even if you have matching damage+ parts of other vehicle attached to yours after having 6 weeks to repair issues.
3) Geico sucks
4) Get rental car coverage, it speeds the insurance company along when it is costing them $ every day they haven't resolved your problems. (I didn't have it).
5) dash cam dash cam dash cam. I have 1 now, I want a second for the rear.
6) have your car aligned someplace that gives print outs with mileage on the print out or else geico will claim your car was always like that.
7) don't change your own tires, and be sure that the official invoices state mileage when you buy tires otherwise Geico will claim your tires are many years old even when the production date is this year and you have matching tire rack invoices, only thing they care about is mileage on official tire shop invoice.
8) geicos website eats any info you upload that they don't like, send everything to them in Macon ga certified mail with video of you putting everything in the envelope otherwise they will not get it.
9) avoid wrecks especially in cars that are worth more than similar cars (aka tdi).
Very best of luck to you.
I thought about going to minimum coverage and putting difference in bank, but I went ahead and got State Farm with a low deductible and rental coverage. I hope I never need it.