FINALLY! With the help of time, penetrant, prying, and the awesome Craftsman punch kit on my work bench that pesky brake arm is now un-frozen. The post and bushing cleaned up easily with some 220 sandpaper and that was followed with a dose of my own blend shop oil (works great in Chris King hubs too!)
On to the brake solution. I have several of the barrel adjuster cores, so I fluted a couple of them to make taps. The solution was tested on the end of the steel tube before cutting it down. So,, with these tools, I made it happen. First I cut the tube to length with the cutting wheel, then used the reamer bit to lightly prep the inside of the tube, then using the punch for pressure and as a guide, threaded it, using up two of my homegrown tools. After that, a little blue loctite and the punch-push with the 8mm wrench set it home. Easy Peasy
One final note on the subject, be sure to bevel the inside of the tube end of the barrel adjuster core to ensure the brake cable feed is easy. I could have backed it out and done that, but instead stripped a wire tie, fed it through the tube, twisted it around the end of the brake cable and pulled the cable through.
Finishing the build after lunch.