http://www.homedepot.com/buy/magic-chef-35-cu-ft-mini-refrigerator-in-stainless-look-hmbr350se.html
I haven't picked my fridge up but http://slickdeals.net/f/5467448-Magic-Chef-3-5-cu-ft-Refrigerator-98-Free-Shipping-Home-Depot mentions it can fit a corny.
I think a 5" ID pipe would have to be ~3 feet tall to hold 3 gallons. Then you'd need to cap off one end and somehow create the fittings. A used corny keg only costs $35 so its not worth the time.
I'm having the same problem. I hear a slow leak coming from the gas post, but only when the c02 is connected. You can try some keg lube, but that didn't work for me. Are your O-Rings new?
I bought this deep socket set from Home Depot. It turns out the sockets are metric and the largest one (19mm) won't fit either post. The socket fits slightly better on the out post but its still too small.
It it possible that both posts use 7/8"?