Got the new 7/16 X 12 bolt and got the skewer figured out.
Here it is assembled. The carabiner locks it from coming apart. The bushing at the right end is a slip fit inside the axle and over the threaded end to protect the threads of the skewer.
There is a rod welded to the nut and captured by the pins to keep it from turning.
Here you can see the bushing has a flange on it to keep it at the threaded end. The trailer pulls on this instead of the threads. This is why I couldn't just weld the nut to the trailer.
Then the wife and I tested it some more. Gravel, some trail and interstate. It's still awesome!!