That's enough HP to go 8.60's or better. Any bumps in the track at those points?
Where does the convertor flash compared to the TQ and HP peaks?

On the loss of acceleration in low gear and high gear I would look at fuel delivery, low gear having fuel sloshed into the motor on the launch and maybe running out of fuel in high gear
I would tighten up, slow down, the front shocks also
Is this a ladder bar car or 4 link? I think adjusting the rear suspension to help limit, lower, the wheelie will help also

Well from the distance cant tell much other than it appears to be dead hooked and tripped the 60' beams with something other than the front tire it appears. Looks like the G meter, which I assume is the second graph is shows the same. Converter is WAY WAY tight. Looks like flash is 62-6300 shifting at 77-7800 falling back to 6200ish is simple KILLING it. G Forces will fall steadily throughout the run from beginning to end. The "choppiness" could be many things but doubt it is anything major. Could be the way the recorded is mounted could be how it is mounted to could be tracks a tad rough. By the looks of it its choppy the entire run..Wouldn't read a lot into that. Plenty to fix with the dead hook and converter for now Id say.

FWIW here is a more typical data log of a G Meter, also shows driveshaft and engine rpm