Adjusting your hitch to restore that 100lbs back on the front axle of the truck will probably help. You are towing a very large trailer with your Suburban and will never get rid of the bow wave effect completely. As long as you have your hitch adjusted correctly, the trailer loaded with the proper amount of hitch weight, the tires aired up to the proper amount, and no unusual suspension/alignment issues you have done just about as much as you can to minimize the effect of passing trucks.
The only other way I know of to cure that problem is to purchase a projection point hitch like a Hensley hitch. It will minimize the bow wave to a very slight nudge that will not affect the steering of your vehicle at all. The downside to the Hensley is that it costs quite a bit more than the hitch you have now.
I would try to get everything set up correctly and see how it goes. No need to spend a lot of money on a new hitch at this time in my opinion.
Barney