Why isn't my refrigerator getting cold?
Alas, the refrigerator is dead.

That smoke was the refrigerant escaping.  Theoretically, you can patch the hole or holes and recharge it.  But that will cost more to get right than buying a new one.

Next time you need to defrost, turn it off and let the ice melt.  This will take an hour or two at no risk to the refrigerator.  If you need to do it in minutes instead of hours, use a hair dryer.