Microwave wiring requirements

Thanks in advance for your replies. This one is challenging. A few days ago, I was using a grounded electric staple gun plugged into a grounded extension cord in a bathroom receptacle. I worked for about an hour, then the power cut off to all receptacles on the circuit. Not sure where the fault might be, I checked all parts of the gun, all plug connections and the breaker…all were fine. I unplugged & replugged the gun into the same bathroom receptacle and it worked again for about 10 minutes… then once again all receptacles were off and have been since. Breaker is still not blown. Before this, all receptacles on the circuit worked. I had never tested the circuit to ensure it was wired correctly. To investigate, I used an electrical tester on the bathroom receptacle. In hot & neutral…no light. In hot & ground…got a light. In ground & neutral… got a light. Based on this, I put an ETCON Model CT101 (to test for properly wired circuits) into the receptacle. I got a reading that said “Hot/Ground reversed”. I plugged it into all other receptacles on circuit…same reading. I then unplugged all elements from all receptacles on the circuit, with the exception of a bathroom wall light also on this circuit. Circuit still read, “Hot/Ground reversed”. The circuit went from working fine to “Hot/Ground reversed” without any apparent change in activity. I have no power current on the hot lead, but there is definitely current on the ground. If I turn off the breaker, power goes out on the ground. I checked other circuits in the house, everything else is fine. Any recommendations of what to do next?

I have a light on the outside of my house. It is controlled by a switch on the inside. I want to be able to turn the light on from the outside. I turned off the power, took the fixture down, drilled a hole and installed a small rotary switch on the fixture. I connected the wires, turned the circuit breaker on and trying various combinations of pairing the wires received the following results. The circuit breaker tripped when I turned the light on from the inside, reset the breaker and it tripped when I turned on the light from the outside. At one point the light was on and when I tried to turn it off the breaker tripped. At one point it didn't do on and the breaker didn't trip. I knew it was getting power because the inside switch is lighted. This is an old house with old wire covering so both wires look black. The light fixture has a black and white wire plus a ground. the rotary switch has two black wires. The wires coming out of the wall to the fixture are also old wiring and both the wires look black. I'm thinking that the switch doesn't work, trips breaker because of the switch on the inside which is still connected. I thought that if I kept the switch on the inside in the on position all the time I can control the fixture from the rotary switch. If your confused, I worked two hours on this and still can't get it. If I remove the light switch from the inside, what do I do with the two wires. I don't know which one is hot but intend to get a Greenlee Voltage Detector which I saw mentioned in an earlier posting. So sorry for the long message. Thanks in advance for any help.