gdog,
Don't give up on that Huntsman, it is one of my favorites. I too, use the .25 ACP plug and wont be going back to 209's or that plug removal tool. You could modify your plug tool so a socket would slip over it, or by welding a nut to the top to give you leverage. If you weld a nut on, make sure you only weld on the inside to keep the outside clean for the socket.
Use Keith's method of boiling some water in a tall pan. Set the breech end down into the water geting it good and hot, that should do the trick. It might take a couple attempts, but heat is your friend here. You might need a padded vise to hold the barrel, and use a large Phillips screwdriver for the breaker bar while holding the tool in place. It will get better.

If you ar looking to get the .25 ACP plug, make sure to measure yours (when you get it out, of course). The 2002-2004 24 " barreled Huntsmans used a 7/8" plug, the 2005-2007 26" barreled guns use a 5/8" plug, I think. If the first two letters on your serial # are NS=2002, NT=2003, NU=2004, NV=2005, NW=2006, Huntsmans were discontinued as complete rifles in 2007, but barrels are still offered in the Barrel Program.
I have a 2003 24" SS Huntsman with the 7/8" .25 ACP breech plug, added a synthetic Monte-Carlo stock and scope for Michigan. I use the standard stock, Williams WGRS Peep Sight, Harris bi-pod for Colorado.
.25 ACP Originator (Canada)
http://www.prbullet.com/nef.htm.25 ACP distributors (U. S.)
http://www.bpbullets.com/thompson%20center%20omega.htmlhttp://www.thebuckskinner.com/breech_plug.html