Do you have plenty of front travel and very light T bars in it? Shocks very loose? That is a good place to start retuning. Making sure your carb is set up properly is very important,so that should come first. Then you can move to the back.
I run a 15.1 x 33.6 tire with 10 psi. Compared to your car, that is very high. So I think if you start by making sure the front is loose as a goose, tune the carb, then start playing with the back end till it works, you will have a great base to start working with the front end. Then you will be able to judge how much you can do with travel limiters ,torsion bar rates, and shock settings to keep the front down down track.
I don't see any wheelie bars, which are great for providing info on what the rear axle is doing on launch.
If you can video the back of the car and watch that rear axle frame by frame, you will learn a lot. You may need to add something to the rear that will stick out the back of the axle so you can better see what is happening.
A video camera doesn't take enough frames per second to catch the speed of the rear axle properly. Things happen so fast 33 frames per second isn't enough. But by taking multiple videos and studying them several times, you will see what is really happening. Good luck with it!