Good news, we have reached the last update needed for this saga!
The 50% water replacement seems to have done the trick, combined with a 2 quart dose of Jack's Magic Purple Stuff. The tint of the water looks notably lighter and more of a pure blue than a bluegreen. No more hair color problems. We are out some expense for the water, plus quite a lot of salt and some calcium, but otherwise we are in tip-top shape with the water now. As a side benefit, TA of our replacement water is much more reasonable as well, so pH is easier to deal with now. Only issue now is that the SWG seems to have blown a fuse or something, possibly because I did not turn it off manually before pumping a bunch of water to waste. Whatever the cause, repair guy is coming out this week and I've got some liquid chlorine to tide us over.
All told, I have blown through about 4 months worth of the expected savings from firing my pool guy. About one month of that was for chemical test kits and startup essentials, about one month was for other chemicals (notably the Jack's Magic is on the pricier side and I went ahead and got supply for the season), and about 2 months to replace and condition about 10k gallons. We'll see what the SWG repair bill ends up looking like. We will probably not reach the break-even cost point for a few months, but likely we will be ahead of the game by year end. The real benefit for this year is the quality rather than the cost. I will not blindly be accruing problems with scaling, metals, possible equipment damage, while my swimmers have stinging eyes and bluegreen hair half the time. So thanks, yall, for getting me up to speed, and hopefully this is where the "Trouble Free" part can begin in earnest.