I'm going to be setting my car up for the next month or 2 for stictly drag racing...I'm on a mission.
Sounds like a good plan. From studying the video, I am seeing a couple of things...
Observations
It seems the tires are slipping on the initial hit, but then grab nicely. This is exactly why you run the bias ply on a manual car; they are more forgiving and will recover from a little spin.
The other thing is the unmistakable "bounce" of the rear suspension, and the subsequent weight transfer to the front tires. Clearly the chassis and suspension are very stiff, which seems to be causing the car to porpoise, or rock, between loading and unloading the rear tires. The line-lock definitely helped to get the tires warmer/stickier. But now that the tires are working better, the suspension (which by all accounts is fantastic in the twisty's) is showing its weakness for controlling the body under hard acceleration. The "bog" you are feeling in the car is more likely to be the effect of weight transfer rocking back then forward, like a wave, killing your momentum from the initial hit.
Recommendations
The softer rear springs will help, as will raising the front ride height. I'm unsure about the correct shock settings, typically you just start with them in the middle, and then adjust from there.
Tire Pressure & Launch RPM
You'll want to consider these two items to be "tune-able" to specific track conditions. This is true for both tire pressure, and the launch rpm. There is no one constant perfect value to be used here under all circumstances.
You have a baseline or start point, but again, this should be in the middle of a range. It is tough to be consistent, especially when track conditions change so dramatically during the course of the day. What works good in the morning will probably not work as well in the afternoon.
My guess is, once you have better body control, the RPM needed to launch the car will probably be in the more typical 3500 to 4500 rpm range. You may also find the tires will work better with a little less pressure.
Conclusion
I highly recommend that as you discover the best drag setup for your car, to limit your changes to only one thing at a time. And, keep a very detailed journal of all variables for each pass.