When the chlorine level is very high, the TA test goes from blue to yellow instead of green to red. You might be be confusing the initial blue as thinking it's green or perhaps it's an in between color, but going to yellow makes it look sort of clear. That sounds like what is happening. As for the CYA level, I don't have an explanation for that but I wouldn't worry about it. You'll know if the CYA is really that low because you'll notice higher chlorine loss during the day and after things settle down you can test again if you want.

As for yellow/mustard algae, you really need to get completely rid of it including behind light niches and under removable ladders where it likes to hide out in shade. Also, all pool equipment that contacts the pool water needs to get into the pool. If you want extra protection, you can either 1) keep the FC at a minimum of 15% of the CYA level (though that obviously can become impractical) or 2) use Polyquat 60 weekly or 3) use 50 ppm Borates in the pool. Though I believe the Polyquat may help, I'm not sure about the Borates for yellow/mustard algae -- I know it helps with green algae).