Re-wiring swing arm lamp so as to remove cord

Simple question, but I'd like someone to confirm this. My non-built in microwave (counter recepticle it's plugged into) shares the same 15A circuit with the kitchen lights, and I'm tired of seeing them dim (and wondering if the house will burn down) every time I cook something. Further investigation revealed a 15A breaker that services nothing more than a rarely used recepticle in the basement. What I'd like to do is take that recepticle off the breaker and tie it in to one of my basement circuts, then run 12/2 from the recepticle back to the vacated breaker. Is this okay? Or should I apply a factor of safety and replace the 15A breaker with a 20A? Oh, and should I throw the main when I'm connecting/disconnecting from the breaker?

I have an Ideal Circuit tester 61-035. I tested an outlet in my home and it showed "circuit OK". The amber and white light clearly lit while the red light stayed dark. No question at all about this. I then tested an outlet in my garage and the amber light is clearly lit. The red and white are dim but they are lit as well. What does this mean? Thanks, Jeff