Hi David, that discussion was a little rushed so maybe there wasn't clarity. Taping off any exposed ends helps, but the real need is to tape off the breakers themselves (or, more officially and better, lock them out with the crimps made for the purpose or simply remove the wiring entirely (what I was in the process of doing before you stopped me due to the kerfuffle with LC). The precise issue is that if there are faults in the wires, which have been seriously jerked around in the demolition process, someone could create a short by inadvertently flipping one of those breakers. So the fix needs to occur at that end.
Just as urgently, please double check to make sure if there's a GFI in the kitchen. There's an electrocution hazard without it. If there is one, as I said it's a little mysterious as to why it hasn't been tripping instead of the breaker, although if the the (new on that circuit) breaker has gone partially bad that might explain it. In any case, as I also said it's pretty much guaranteed that all of those appliances turned on at the same time will draw more than the 20 amp capacity of that breaker, and probably just three of them, so that's the basic ongoing problem. The hot water pot was still in there last night, note, and those are surprisingly high-amperage, so maybe removing it is enough, although the unknown amount of other loads on that circuit from the den area and possible other stuff might necessitate removing two of them to ensure 20 amps isn't exceeded. Given the den situation, some stuff in the upstairs hallway might also be on that circuit, maybe including the refrigerators, so you should check for that..
One slight possibility is that the current #7 breaker is 15 amps rather than 20 amps (it shouldn't have been given that it was being used as a receptacle circuit, but who knows) so you might have a look, and if so there should be a couple other 20 amp breakers in the box that can be repurposed. But the hot water pot still needs to go.
I assume you're aware that as a general matter receptacles and lights are never supposed to be on the same circuit to begin with (I can't recall, but there may be an exception for kitchen and bath lights on a GFI).
OK, I'm officially out of troubleshooting thoughts. But this is all obvious stuff to an electrician. FWIW, I guarantee you they'll tell you the whole thing is a horrible mess and needs immediate rewiring.
Oh yes, maybe add some sort of direct wall support (or ceiling might be easier) to that floating box to make John happy the next time he comes by. You know he'll look. Fortunately everything else we've been discussing is his fault, as it were, since he handed the building over in that condition.
-- Steve