Reading your post (but not all the responses), my immediate thoughts were:
1) Trailer is heavier than you "think" it is, and weight is heavy on the tail, light on the hitch.
2) You did not specify what kind, if any, type of weight distribution hitch system you are using. If you are not using any kind of weight distribution hitch system, with a heavy trailer, lifting, air bag, all that really isn't going to help the weight on the rear tires and the lighter weight on the front tires (causing potential sway)... mixed with a heavy tail trailer.
3) You did not specify if you had any kind of sway control. Even an old fashioned Reese chain link WD system with a friction sway bar may be just enough to stop all the sway. So I'm assuming you do not have any kind of sway protection installed.
Lifting with air-bags, flipping axles, larger tires, inflating tires, deflating tires, all of this stuff helps to keep the tow vehicle and trailer level, but it really does not change the weights riding on the hitch. I think this is the biggest factor.
These were just my initial thoughts. You're putting band-aids on places that aren't hurt when the real problem is bleeding elsewhere.
1) Trailer tongue weight 2) Weight distribution hitch 3) sway control.
