temp wiring

I'm working on my kitchen and just ran a temp circuit. Why is it temp? Well I used an existing wire that had been used to run an AC. The wire is a heavier guage than the romex I used on the outlets. I have three outlets on this circuit one of which is for the fridge. The other two will run odd appliances like the coffee pot, mixer etc. At the end of the circuit I left a length to wire a future range hood.
As soon as I plugged in the fridge I noticed it ran faster and louder than ever before. The fridge bulb blew too. I set the stove timer to see if the fridge would stop running but it didn't in ten mins. So I unplugged the fridge and went back to the old socket.

Anyone know if what I observed were indications of trouble? I plan on replacing the larger wire soon (as in the next month or so) and moving it all to the proper size breaker. This house has some funky wiring and I can't tell the breaker size (nothing written on it) except that it is a double . My box is only 50 amps. Can I use a 15 amp breaker on this circuit and leave a slot open for another circuit? This will be my first time putting in a breaker. The box has the master switch alone in a smaller box before you get to the box itself.

MollyD