IF the microwave is in the kitchen, those branch circuits should stay in the kitchen. Sounds like whomever wired things went the cheap way and ganged lots of things together. As to the CB 'feel'...I suppose it could be a function of how hot the thing got. If there isn't a wiring fault, and it was a long-term overload, it could have gotten hot before it tripped. Most CB trip fast if there's a short, but load it up to max or even above, it can take a bit of time before it trips...this can make it at least warm, if not hot. Overnight, if it had tripped earlier, it would have had a chance to cool down. There could be an actual wiring error, but that would take some careful examination, and can't be done from afar. CB do wear out, but often have a very long service life.