Agree with all the breaker will be replaced. It is factory original, 6yo, rusty as all say and a cheap fix.
Westend - battery shows 12.8 when I connect it to tester on my charger, 12.? when I use my analog multimeter which doesn't have fine enough gradients to be precise.
Wiring is as original and has one line going to this breaker (-ve), another wire (+ve) which is split into two pairs: one goes to the jack (fused), and another goes into an electrical box mounted under the frame. Jack fuse tested and fine per my multimeter. Just starting to pull and check fuses in the converter. Have not tested DC output from the converter as I didn't want to re-connect shore power given issues.