"Test 1: With shore power attached and all of the circuits turned off I still get an AC voltage reading between the frame and the earth. (I am pushing the black wire on the multitester into the ground). I took the cover off the circuit panel and couldn't find any wires touching or frayed. I can't understand how there is any voltage when the main is off unless that circuit breaker is broken...."
Something is still connected to shore power. As uncle bob says, some designs of noise filters in power supplies (like your converter) will put about 60 volts on the ground connection of the power supply. It should be connected to your house power ground by the green wire system in your trailer. That ground should go back to the ground for your house through the 30A wiring (you do have a ground wire in that connection, right?) Even if that is wired correctly, the potential of the earth at the location of the trailer can be different than that of the house ground (typically at the meter) and may still give you a shock. The only way to prevent that is to drive a ground rod at the trailer and connect it to the trailer frame.
"Test 2: I took the batteries out and disconnected the shore power. I found D.C. Power from the red (positive) battery cables to the frame of the trailer. How? No power source. I have an Intellipower 9000 with a Charging Wizard and thought maybe this device has power storage. I mean, even the green light on the Charging Wizard was flashing. The only thing I can think is there is a small battery for the power jack that is connected to the trailer light umbilical. I thought that particular battery gets charged from my truck and was separate from the trailer AC & DC systems."
Power converters typically have large capacitors in them to smooth their output. They will store 12V
for a significant period of time. Turn on a 12V
light and it should discharge the capacitors. If the light illuminates, the converter is still powered which could be possible given that the trailer has been rewired. I'm assuming you don't get the shock if the shore power is disconnected.
Is that battery for the jack, or for the brakes? Sometimes the emergency brakes have their own battery, but that is more typical on things like boat trailers that do not have house batteries. Maybe the PO hooked it up to the jack instead.