Sounds like you're on top of things, but yeah, the steering stabilizer could be part of the issue, even though it's not always the root cause. Since you've checked torque and play, and your caster seems off (5-6° isn’t ideal), I’d say the alignment and possibly the caster need more attention...
that -18 offset with the 315s will stick out a bit, maybe 1-2 inches. A 2-2.5" level should work to clear everything and still keep some rake for the tent. The suspension might wear out a bit quicker, especially control arms and steering, but nothing too crazy.