Tire pressure dilemma

I recently got new wheels and tires for my 02 Limited. Went from stock 16” wheels and 265/70R16 Nexen Rodian AT Pros to LT265/65R17 BFG KO2s and 17” 03-09 4Runner wheels. The Nexens had a max of 51# and I ran them at 40# they did fine. These new LT BFGs have a max of 80# and I have no idea what to run them at.
I found a pressure calculator online which used the GAWR and tire specs to recommend psi, (pic below). I used the max GAWR on the door sticker and the max tire weight and pressure to calculate. If someone could tell me if these figures look right or if they’re completely off I would greatly appreciate.

 

It looks reasonable to me, although I'm unclear how/why the rear axle is 800lbs more than the front axle is, which is where the engine is?

That said, I've seen the "chalk test" is supposed to be the most reliable way of determining "correct" tire pressure.

 

Here is the door sticker with the GAWR on it

 

I'm not an expert.. but I think those are "max" numbers?