Congrats on your new project. First thing I would do is cover the exposed black and white wires. that looks to be a potential shocker. Maybe wire nuts will help.
I think the battery charger is a common fix for broken converters. If the battery is good this can werk for awhile until you can get a new converter installed or forever if you so choose.
The way to learn your circuits, both 110V and 12V, will be to turn everything on and then turn off breakers and remove fuses one at the time to see what shuts down. that way you know for sure what you have, just in case someone changed something.
if you have roof air conditioning one of the circuit breakers will be for that. The roof air will not run on a drop cord from a house 15Amp circuit. You will need 30Amp or better to run that.
Nice video. We like pictures and videos. Makes it all clear. Have fun with your projects.
Beverly & Jim
1991 T-2363 Solaris