Pool chemical balance - 0 FC and High CH, CYA
A high CYA (cyanuric acid) will cause the chlorine levels to appear lower than they actually are. Unfortunately the only way to lower high levels of CYA is to add fresh water. You ideally want the CYA level to be in the 20-40ppm range. CYA is the stabilizer which slows down the process of chlorine evaporation due to sunlight. Trichlor tablets have stabilizer in them so you don't need to add any yourself. Likewise, shocking your pool with trichlor will also add stabilizer. CYA levels are usually lowered during the season via splash out.

There's nothing wrong with having high levels of CYA, you'll just have a hard time monitoring your chlorine levels. If you're close to the end of the season, I would say do nothing to correct the problem and then drain your pool when you close it, add some fresh water for the cover to sit on and let the rain fill it up in the spring. If you want to fix the problem now, drain your pool and refill it with fresh water. The amount to drain is dependent on the current level of CYA and the target level.

Another observation is that both your Total Alk and hardness levels look too high. TA should be around 100. Your hardness may be right on the verge of the high range. Personally, I'd bring it down closer to 300-350. Draining your pool and filling it with fresh water will accomplish this as well.

When it comes to adjusting chemicals, the Taylor recommended order is: 


Total Alk 
Calcium hardness
pH
Chlorine