Do you have the thread cap/protector of the gun once the factory brake is removed?
If so, get a blow torch with MAP Gas fro your local hardware store and use the rosebud nozzle to heat the muzzle brake to almost red hot.
This should heat up what ever thread locker that was installed at the factory.
With a leather glove wrapped around the muzzle brake and a pair of channel locks grip the brake and twit off.
Righty Tighty , Lefty Luci thats for you to figure out

I am not a gunsmith nor do I profess to be one and last but not least I like to fix things till they break...
Seriously though, I had a local g/s remove the brake on a 9mm PCC that was installed and thats all he did, heated the end up closest to the threads and twisted it right off and spun a cap on for me that he made.
That took about a week and a $50.00 bill to cover his costs.
Rob