The saf t steer does not help with sway. I have one on my Hurricane and it helps with centering the steering but does nothing for sway. Neither did the sumo springs I installed. The sumos do smooth out the jolts from bad roads. I did the CHF to help with sway, but honestly, driving a box that is is 30 x 12 x 8 one has to expects some sway.
You are on an E-Series chassis. I had an Outlaw 29H on the E-Series and installed a Roadmaster Steering Stabilizer, Hellwig Front and Rear Heavy Duty Sway Bars and Front and Rear Sumo Springs. It cost me ~$1500 doing the work myself.
In my opinion the stock suspension on an E-Series chassis will not adequately support a motorhome 25' or longer. As a result you will get sway and drift. Before adding the above changes, my Outlaw drifted and swayed and was a white knuckle driving experience and fter about 5 hours of driving I was worn out. Once I added the above items it was much better to drive and I could drive 8 hours without being worn out.