With full fuel the aircraft will be structurally limited to less than 5.5 G at a typical empty weight.
6.5 G is available at a gross of 50,000, resulting in a total lift of 325000 pounds. Divide your gross into that to obtain your max G assuming that you plan to observe the structural limits. It also shows the variation in performance based on weight.
It's interesting that the Ps charts don't show the G limits for the actual gross weight listed on the charts. They show the max G limit of 6.5 instead.
Buffet is a fantastic cue for fighting the aircraft, but it takes finesse to both learn and apply while under pressure.
Edit- for max acceleration, unload to .5 G. Don't go to zero, you'll run the engine feed tanks out of fuel. If you aren't accelerating, then you have too much G on the aircraft. Frankly, your numbers sound like you are in mil power or less. You are getting full AB in your Peterbuilt, yes?