28 psi is more appropriate for a 33" tire, 24-26 is about right for a 35x12.50 when supporting a Wrangler. 24 psi when the TJ is only lightly loaded, 26 when it is fully loaded.I deflate to usually 15 psi, might try lower next time, and inflate to 28 psi, on a 35x12.5x15.
And when offroad, 15 psi isn't airing down all that much where a 35" tire is concerned. The bigger the tire, the lower the pressure that should be run. Before I got my beadlocks, I was regularly airing my 35" tires down to 8-10 psi on standard wheels which is what they're commonly run at offroad. The reason to air down is to increase the tire's footprint size and to allow it to flex and conform more easily to uneven terrain. All in the interest of better traction so the drivetrain doesn't have to work as hard to get the Jeep through difficult terrain.