So even after draining half, you are still at CYA over 100? Wow! You will have to either do one of two things:
-- Do another drain and refill of 1/2 to 2/3 water again to try and drop cya further or
-- Run higher than normal chlorine levels to compensate for the high cya. That would mean that you would have to keep your cl between 8-15 ALL the time and when you need to shock, you'll have to take it up to 25.

You need to get some bleach in there and bring your cl level up ASAP.

No more tabs or powder shock for your pool as they both have cya in them and yours is WAY high. Stick with bleach.

How does the water look?