Traction problems

Your rear is unloading after initial launch and spins the tire, then grabs again.
This is what I would do with the parts you have.
Front shocks set to 90/10 Trim the upper control arm bump stops to allow more downward travel.
Rear shocks set to 70/30. You want the shock to extend easy to plant the tires. Firm rebound keeps them planted.
If your snubber is adjustable set it to within a 1/4" to 1/8" with driver in seat race trim.
Lowering blocks would also help weight transfer.

I run 255/60/15 MT drag radial 18 psi, small burnout just to clean.

Here's a video of my car. At :25 the car is stage and on the snubber. At ;28 the tires are planted and stay that way.