Difficulty Reducing Tongue Weight

Your numbers work out okay, and airing up/lower nose has made a difference you can feel. Those tires (low profile,less squirm) and aired properly for towing, should work. LTs in load range E, yes, better, but so is heavier duty truck, or smaller trailer. IMO, you may be towing a little fast for that rig, but you know your comfort zone best.

Hope handling has improved enough for your satisfaction! Good luck,

Jerry