Just saw something that makes sense.
Jacob, try turning the extinguisher upside down.
The reason for the tube is to get the liquid co2 from the bottom of the extinguisher where it gathers - handy for putting out fires it seems.
Turn the extinguisher upside down and it will gather at the the "valve end" and you'll get the gas from the "bottom end", which is now at the top <!-- s:) --><img src="{SMILIES_PATH}/icon_smile.gif" alt="

" title="Smile" /><!-- s:) --> - handy for dispensing beer it seems and not breaking your regulator.
Will be interesting to see if this solves your ice on your reg issue.