It should be OK, as the compression seal is formed between the sleeve, head shims, and head button. As long as you didn't damage that area with the grinder, you should be good to go.
Sealing the edges helps prevent delamination and stress cracking, which carbon fiber is somewhat prone to. It's a good idea not just for aesthetic reasons.
I run a 125cc Ofna tank in the stock location, and it works fine for bashing. You get used to re-fueling more often, most of the time when I pull the truck in to re-fuel the tank is still 1/4 full or so. It is also the only setup that positions the tank out of the reach of the upper shock bolts...
Low tensile strength and much more elastic than aluminum alloys/CF, not the material you want your TVPs to be made from.
My 1st material choice would be a good, artificially aged aluminum alloy such as 6061-T6. Fairly lightweight, strong, and impact resistant. Quasi-isotropic CF would be my 2nd...
You need a calibration weight, and the process is very straightforward.
They come pre-calibrated from the factory though, and they rarely need re-calibration.
It appears to have a decent sized pilot valve, so the main valve should actuate fast, and the report should sound like a pretty loud crack. I've built a few pneumatic cannons myself, but nothing of that size.
You overpaid. I have the same scale, but with 0.01g precision and the same maximum capacity. I paid $30 on eBay.
They are useful, but I don't really use mine for R/C, only pyrotechnics.