I might be able to lend a bit of help but then we do have to admit that Winnebago has gone into what I call a "bait and switch" setup on electrical info as they do not give us the info we need but lots of "Show" junk that makes it look like they are trying!
I assume you have found your drawing in the set and gone to the 12Volt:
https://www.winnebago.com/Files/File.../000172590.pdf
Not sure which serial number you have, so this is from the first group with 7th digit of 1! But it will do as example for you to choose the correct set?
A bit of place to start?
Click these snips to get a better view or go direct to drawings.
On the breaker we can get an ID for the circuit here!
This should fit with an ID that should be stamped on each wire:
There is a chart here giving the "from" and "to"of each wire ID:
https://www.winnebago.com/Files/File...ical_guide.pdf
This chart can let us dig some info out of the bits they give us.
Looking at the drawing, we get circuit ID of JB.
Looking at ID chart, we can hit "ctrl" and "F" at the same time to bring a dropdown where we can input "JB". This will bring a list of every place where JB shows in the list. In this case it gives us what wire JB does!
That verifies that we have got the right ID!
Another way to use this chart is by putting in the item we want info on, like "furnace" and we may get it to spit out wire ID's involved in the furnace. Small help but if looking at a bundle of wires, we can often find which is battery and ground! Big help, there!
There is a bit of info on the drawing for wire ID at the thermostat which may help?
But I might have thoughts on part of your thinking. Much of what you have done sounds correct but I might question the part about high resistance from a fuse as I do not find that correct in many cases. I think what you are saying means the 2000 ohms is a problem, not a fuse?? High resistance open, perhaps? Something damaged enough to not be totally open but not totally good either! High enough resitance to make it heat instead of passing the current and voltage as it should? I might recommend checking more closely there.
But I may also be missing what you are saying as it is not specific enough for me to follow close enough to feel that I'm reading you right!
I think you are saying you have it isolated to working when an item is disconnected but blows fuse when that item is connected? Sounds like you are close to the right spot, so maybe dig deeper into what that one item does and which wire then is the problem.
Thoughts on possible problem but based on guesses?
I might look for that high resistance and wire that gets hot as something like a staple through a set of wires or maybe where it has scraped along a metal edge? Going into the roof top unit is one potential that comes to mind. Maybe where the wires go through a metalclamp into a box?
If you can get it down to one specific wire, it may be possible to run a new wire between two points and just abandon the damaged wire.
But repair thoughts are getting way out in front of finding the trouble!