As a former Gladiator owner, they are just too damn big. It's great that they are basically a four door Wrangler with a bed, but that also means they weren't designed to be a truck day 1. They should have redesigned the whole thing.
I have a D ring receiver as well. Don't forget about friction of the two steel surfaces, versuses just a metal pin. The d ring receiver will be stronger than just a soft shackle on a pin.
I air down to 18. That's my magic number on any 4x4 I've owned.
Your tires will tell you what pressure they like. If too high they will tramline.
Feel free to start at max pressure of the tires or at 39 and decrease the pressure to eliminate tramlining.
A spacer lift isn’t beneficial for off-roading anyways. It will give you more body clearance, but no further articulation and suspension travel. Plus as we are seeing they mess with geometry.