Oh man this is giving me some flashbacks.
As you can see I had a similar experience 2 years ago getting rear ended in my B4V and the subsequent insurance fight that I dragged out close to 6 months.
I was the middle car in a 3 car incident on a mountain in Colorado, a Prius (of course) stopped to look at deer on a downhill 2 lane mountain road shortly after a blind corner. I stopped about a car lengths behind him and layed on the horn - he just sat there. I watched in the rear view mirror as the car behind me came around the corner and didn't even try to swerve or hit the brakes - nothing - just plowed into me. He was
looking back over his shoulders at said deer - while driving down a steep mountain road, right after a blind turn. Totaled his ex-wifes Toyota Sequoia (who was with him), and was driving without a license as well. First accident I've ever been in and first time having to deal with insurance at 28 years old. My most prized possession VW, I still get worked up thinking about it too much.
Here's the for sale ad and details of my B4V I bought about 3.5 years ago.
He was asking 9000 - I paid 7500.
http://forums.tdiclub.com/showthread.php?t=430927
I don't remember the exact numbers they offered, something around 1500 I believe, def under 2000 and totaled. Same issues you are having - no comparables - they kept just coming up with regular old MK3 cars, no wagons, gasser stuff, it was absolutely ridiculous what they were comparing with through their CCC One crap. It was an infuriating time...
They kept being so condescending when talking about the value.
I mean it was literally a 20 year old VW with 300k miles on it, I get it, but a vehicle like this one and the mods it has and the excellent condition even at 300k, there aren't any algorithms or formulas to put a price on it.
I actually got NiceCars (google them) to help me out with an appraisal and they were very nice and helpful - they did their due diligence. They sent lots of documentation and paperwork in showing people paying 10-20k for these things, etc, but the insurance just came back and said well those are fully restored examples - mine wasn't, so they weren't comparable. Not sure how much more restored you can get when you see all the pics and documentation I sent in about it. Everything worked fine, nothing broken or missing, interior was perfect, paint was great, southern car whole life, extremely well maintained - nothing mattered - all they saw was 20 yr old VW with 300k miles.
Long story short, I basically just ignored them and kept driving the vehicle for the next 6 months with some zip-ties holding the left side rear bumper cover in place. All the tail lights still worked, the hatch still opened and closed, there was nothing "totaled" about it. I made them well aware of this fact and my intention to fix the car and keep driving it regardless of how long this drags out - no huge deal for me. They would call probably once a week - I ignored them most of the time, but every now and then I'd answer and just end up all pissed. I finally told them look, I know what it is worth and I'm not trying to get more than I paid for the thing, I just want a fair market value and I gave them a number of 6000. A few days later they called and said they'd do it minus the salvage value. So after 6 months of being stubborn, I ended up getting a check from them for 5700 and avoided the salvage title.
It's still in the driveway with 313k and I drive it all the time - have a hatch and all the parts to fix it, but haven't taken it to a body shop to have it all fixed up as best as possible due to life changes / disposable income. Like I said it still functions fine, it is just cosmetic really, one day I will get it fixed and make it look a little better in the back.