Mercury & Willig - I guess slow and steady will win the race

Merc update: I have been blissfully ignorant for the past fifteen years that there is a bad habit called "balking". That's exactly what Mercury is doing, and thanks to the internet, I've now done quite a bit of reading on it (and found it in some of my horse books too).
According to Cherry Hill, balking is "refusal to go forward often followed by violent temper if rider insists" and it is caused by "fear, heavy hands, stubbornness, extreme fatigue" and the treatment is "Curable. Review forward work with in-hand & longeing. Turn horse's head to untrack left or right. Strong driving aids with no conflicting restraining aids (no pull on bit). Do not try to force horse forward by pulling -you'll lose."
Many of them mentioned the "violent temper", but none of the causes apply, except, dreadfully, stubborness.
I talked to my friend J today, and she said that her horse does it too (but not "violently"), about 2-3 times in the 10 years she's been riding her, so she gets a wild hair, tests her authority with J, and then they go back to work. J says she gets off and lunges her until she's in a froth (what I've been doing! yay!) and if she's on her and can't get off, turns her head to spin her if she tries backing/sideways movements. She says it is NOT inappropriate to get off when they're being ridiculous becuase otherwise they are learning that they can indeed boss you around.
She suggested a week off, since Mercury has totally pushed my buttons and I'm pissed, with lots of lunging, and then just turn his head and lunge the bloody hell out of him if he tries it again as long as it takes.
She also thinks a month "with a cowboy" would do him some good, and that he could still find an appropriate home where he won't feel like he needs to test. I think it's going to be much more difficult now, but I'm feeling better.

Today Willig just got turn out on grass. At first he looked like he was frolicking and having fun, but I think it was actually more nerves.
Sigh.
Regardless, he cantered and bucked way off in the field, far away from the gate, and once I came back in (I had walked the dogs from the car to the adjacent turn-out and back, and with Odin, that takes forever), he went back to eating grass instead of running around. I actually consider that progress. He wasn't a wild man crazy.

The good news is that willig has NONE of the Cherry Hill "bad habits in horses" which include, in addition the dreadful balking, "barn sour/herd bound, biting, bolting when turned lose, bucking, can't catch, can't handle feet, halter pulling, head shy, jigging, kicking, rearing, running away/bolting, shying, striking, stumbling, tail wringing". That's pretty cool. And Merc's balking appears to be on the very mild end of the scale from the stuff I read on the internet. Still - how do I NOT know these things? I know basically nothing about horses.

I'm going, in the days that already don't have enough hours, to try to start doing yoga and some strength training at home. My legs are getting fat and I'm losing flexibility in my old 30's. (I also have GOT to find time to run and bike. I'm going crazy with the routine of work, sick dog, bad horses, try to keep house a tiny bit clean.)