The class 4 on my '15 Ram 1500 is limited to 1100 lbs. I don't notice anywhere that specifies that a weight distributing hitch is required with that weight. The 500 lb limit is for the bumper mounted hitch.
To the OP, regardless of that auto-leveling air suspension, I would use a weight distributing hitch. Just remember that tongue weight counts against your total payload weight for that truck. That heavy of a tongue weight combined with the weight of the passengers in the truck will be already getting close.
For the record, I have a similar truck and a trailer with a similar or heavier tongue weight, and a similar Champion generator that I'm seriously considering adding to the tongue. I may occasionally exceed the payload/gross vehicle weight rating, but I won't even be close to the max gross axle ratings. Since the hitch is rated to 1100 lbs, I'm not even sweating that part.