Hey there!
I posted virtually the same question a few days ago. I have bought a pair of these locks and will lock the chains behind the truck. I figure backing the trailer into a physical wall is enough impediment to having the car stolen off the trailer, and the locks will deter someone from attempting to make a racket and unhook the trailer (as /u/stainedhands pointed out)
Get a third and secure the door and don't worry so much! Park in well lit, chain motels near major highways. I'm staying at a Hilton owned property with ample room on the back lot to back into a space and prevent the car from being rolled off the trailer.
Lots of people like to use Bluetooth to radio adapters such as this: https://www.amazon.com/dp/B018E0I01I/
They’re inexpensive and work pretty well. I even have an old beater car that I don’t want to bother putting a new radio in so I use one in it.
There are 2 different things those could be used for.
If they are for trailer lights, they're going to be for either a 8pin or 6pin configuration (both pictured here on amazon). Uhaul no longer sells this as this style is no longer used for trailers. It was never properly standardized so the pins can be in different orders on different vehicles/trailers. If you test yours and figure out what each wire is for, you can order this extension, cut off the unneeded side, and use heat-shrink butt connectors to attached the trailer wires to right pin. Though, i would recommend replacing what you have with a standardized plug (7pin or 4pin).
Those could also be for accessories, though its unlikely due to the vehicle age. If that's the case then those wires would be 2 wire circuits (1 wire's ground, the other is hot) that can be used for auxiliary power. Nowadays they're often used for led strips and lightbars, but its actually hard to find anything still using that plug.
Again, id recomend getting a new install. Less hassle and probably less expensive in the pong run.
I dont have much else to move other than a electric keyboard similar in size to this one. Do you think 1 trip is good enough in this case?