A few observations:

First, the Park Video: it seems unimaginable that the Park mechanic refers to the sprockets as cogs. That's not an unusual mistake and lots of people do it, but you'd think that a Park expert would name them correctly.

Second, like Jon, I have broken many a chainwhip on stubborn (mostly Suntour) threaded sprockets. I've also broken more teeth off Suntour sprockets then any other brand.

Third, Jon and his cheater bar and pipe wrench: Fantastic work! I've not attempted this approach, and will give it a try the next time I'm in the workshop. I have plenty of !@#$% stuck broken tooth threaded sprockets preventing removal of other perfectly usable ones.

Fourth, consider looking for a Bicycle Research or similar freewheel vise. They are far superior to the Suntour four prong model pictured above. They use a protrusion which fits into the threaded area of freewheel and then have chains which can engage the largest sprocket. Mine even has a threaded hole through the center of the protrusion and I was able to find the correct bolt at my local ACE and using washers and a wingnut, I can secure the freewheel even further.