Can I use weight distribution hitch on a 2009 RX350?

[MartinNorth]

Hi, I am new to the forum and have a question on my 2009 RX350: Can I use a weight distribution hitch on this vehicle to pull a 2000 lbs (dry weight) camper trailer from southern Ontario to the Rockies and back? Or would the torsion from this type of hitch bend the frame or snap the bolts? The purpose of the slightly stronger weight distrib hitch (4000 lbs vs 3500 for my existing hitch) would be to level the Lexus, reduce trailer bounce on bumps, and reduce trailer sway.
Has anyone used a weight distribution hitch on their 2009 or older RX without problems? The available Curt #13530 weight distrib hitch (rated to tow up to 4000 lbs with weight distribution) is explicitly stated by Curt to fit the 2009 RX350 (among other models and years), but I can't find a statement anywhere that it can be used as a weight distribution hitch on the 2009 or older RX350 instead of just as a regular hitch. 
My situation is this:
- The trailer GVWR is 3500 lbs (unloaded weight is only 2000 lbs).
- The trailer's dry tongue weight (hitch weight) is about 220 lbs.
- The current hitch receiver installed on the vehicle is a factory model typically installed by a Lexus or Toyota dealer. 
- The installed factory hitch as far as I know is NOT rated for use with weight distribution bars (torsion bars). The sticker on the hitch only mentions the regular towing limit of 3500 pounds and does not mention a weight distribution towing limit.
- A local hitch installation expert believes the frame of the RX350 probably was not designed to accommodate a weight distribution hitch until 2010. Our RX350 is a 2009. The local expert, who looked at our existing hitch on a hoist, believes we won't gain enough by replacing the hitch.
- The vehicle as it is now is rated to tow 3500 lbs with the factory tow package which I have, and rated for a max tongue weight of 350 lbs.
- But the trailer currently does sway and bounce some when we tow it. And the Lexus sags several inches in the back. I know the sway can be corrected by an antisway bar and probably be improved by raising the ball mount on the vehicle, which is currently about 2 inches too low for the trailer.
-  The after-market Curt #13530 weight distrib hitch mentioned above (rated to tow up to 4000 lbs with weight distribution) is attached to the frame by 6 bolts rather than the 4 bolts that I think are used for the current factory hitch. The threads on the frame are cage nuts (captured nuts or maybe they are welded on, not sure)

So to sum up, I would like to know:
- Can a weight distribution hitch be used on the 2009 RX350 without bending the frame or breaking the bolts holding the hitch to the frame
- Does the fact that Curt designates its weight distribution hitch as fitting my vehicle mean that it is intended to be used as a weight distribution hitch on my vehicle, or just as a regular hitch?
- For a trailer that may weigh 2,800 lbs loaded, is it overkill to replace my perfectly functional non-weight distribution hitch with a weight distribution hitch that adds 500 lbs of towing capacity and 50 lbs of tongue weight capacity. The cost of the new Curt hitch would be about $ 240 Canadian to me, plus maybe $30 for a torque wrench to install the hitch myself.

Thank you in advance for some expert advice on these questions.