I am sorry to hear of the frustration, but I understand. I'm sure your high cya is probably from years of somebody using trichlor tabs in this pool. There should be some kind of note on the label alerting people to the fact that if they use trichlor for a long time, they will have significant cya buildup. It would save people from being in the situation you are in. A lot of other people have the same issues. But, then they wouldn't sell as much of their product, would they? The almighty dollar.

I don't know if you just want to bite the bullet and do another partial drain and try and get that cya down more or if you just want to live with it. I think if it were me, I'd just go ahead and keep doing partial drains/refills until I got it to a more manageable level. A big pain in the butt, yes, and the cost of the water. But, then, it will be done and as long as you stick with chlorinating with bleach or liquid chlorine, you'll never be in this situation again.