FYI - this thread is likely to go down the 'overweight' path very quickly. When you go to the scales, you may be surprised at what you find. It is highly likely that you are near or over your GCVWR on the 2.7, and you may or may not be exceeding payload depending on your configuration and set-up. That said, for the short term issue you are trying to cover, here's a few things to consider...
First - are you sure you are dialed in with your WD hitch? The fact that you are 'sitting level' doesn't necessarily mean anything. You need to do the before and after measurements of the wheel wells to make sure it is transferring enough weight off the rear axle. Again - if you scale properly you will get some insight here as well.
Second - are your WD bars also sway control? They aren't necessarily one in the same.
Third - how is your tongue weight? Again, scales will be necessary here, but you want to make sure it is sufficient. The general range is 10-15% of total trailer weight - I find ours is best around 12%. If you are way out of line on this number, it can cause problems.
Fourth - How are you loaded? You said that you only had clothes for 2 in the trailer. Is that all you had, or did you have a bunch of stuff in the truck bed? You are likely pushing your GVWR, which means that a heavy load of gear in the bed could be a part of the problem as well.
All in all, I would start with these things. Make sure you have your setup dialed in before you try to branch out into band-aids. Airbags are very helpful in some situations, while people seem to debate whether or not they actually benefit with sway (I've never used them, so I have no opinion). In either case, that's a lot of money to invest on a truck you'll be dumping soon - so I'd work hard on making sure everything else is covered first!
Start at the scales - it will tell you a lot.