My experiences racing 1/12th on asphalt.
Start off with a relatively safe setup. By "safe" I mean a soft setup that is manageable with slight a understeer. Everything you've done is the opposite. We'll get you back on track.
A starting setup that I found worked for me.
Center spring - Associated Blue spring or equivalent. Try running the softest spring possible and work from there. Hardest I've gone is Associated Gold.
Center damper oil - 400 CST
Side springs - Once again try something soft, like Associated Black or equivalent. Try going to Olive.
Side tubes - 10K
Front springs - try the kit springs and work from there.
Dynamic caster should be 10 degrees. Very rarely would you run 5 degrees on asphalt.
Front droop 0.5 mm, rear droop 1.5, pod droop 0.4 mm.
Camber -1.5 and toe out at 1 degree.
Upper and lower arm geometry should allow for a lot of camber gain. Cristian can assist you will those settings.
As mentioned before, pre-loading does not increase the spring rate. It only increases the ride height and removes droop.
Tightening the differential isn't the best idea either for low grip. I would loosen it off until it doesn't slip under load.
The V2 looks like a killer car, I just don't think you were going in the right direction with the setup.
Not to worry, it's all good. We've all been there.