Thanks to Carlos, N4IS, for his continued support, by email and on the telephone.
Today I replaced the coax feeders with CAT5 twisted pair. I ran the wire inside the boom and the mast. This should eliminate most if not all chance for common mode noise pickup on the feed line to the preamplifier, as it’s insulated, and because twisted pair is designed to minimize noise pickup.
Using Polar plot, I was able to collect this table that clearly shows that the antenna is working mostly as it should. I did my best to rotate the antenna by hand at a constant rate. For the test I used a 500W AM station about 2 miles away. There are some small lobes to the rear that is probably interaction with something nearby.