I can't help with the trailer. This I caught, you said that Toyota says you have a weight distributing hitch. I venture that you do not. You have a receiver that is heavy enough to make use of a WDH.
The WDH is the hitch head component that fits into your receiver. It will consist of the shank,the drop , the hitch ball usually 2 5/16 two bars and chains and the corresponding bracket fitted to the A frame of your trailer.
If you look at your receiver there usually will be the statement
"Do not exceed X00 lbs/x000 lbs wdh".
maybe you know all this, but with the statement you made I would hate to think of you dropping your trailer on a bare ball and thinking you were good