Fridge Drain Plug Problem:

I just lit my fridge on propane for the very first time.  It took a while
and so I was trying to follow advice I found in the message archives about
blowing air through the drain plug.  Unfortunately the PO had not lined up
the threads on the plug and it was nearly impossible to remove the plug.  I
first tried with a screwdriver and it broke the thread off the nut!  So I
had to resort to using an adjustable wrench but was able to get it off
eventually.  I'm worried that the threads in the drain tube might be messed
up from the drain plug having been screwed in incorrectly.

If the threads in the line are messed up, is there a way to fix them or an
alternate way to plug the drain?
Is it possible to get a new plug somewhere?

Propane Tank Problem:

When shutting down usage of the propane camping equipment, I light the
stove and then close the valve at the tank.  I expect the stove to burn off
any remaining propane in the lines, but twice in a row the burners have
continued to burn indefinitely, once at full power and once with just a
small flame.  Both times I opened the valve at the tank slightly and then
closed it again and the burners went out.

Am I correct in thinking the propane tank valve is beginning to go
bad?  Are these replaceable?

Thanks!

Marc