Well I used my kids as guinea pigs and think I solved the trailer hitch problem, but I still don't have a set of cheap wheels! Using fronts off of other bikes

I had a racking issue between the ball and the hitch arm because I need to remove the arm to get from the back yard to the street. I added crush sleeves between the square tubes so I could tighten the snot out of the bolts.

The saggy hitch issue was solved by adding a stout steel bracket below it. I think I can put my rear rack back on now because everything stays where it should.

The hitch swinging around my seat post was solved by making my own adapter with nice ugly teeth that bite into my seat post.