As you found out the CYA test is very subjective. I usually use a white fluorescent desk lamp to illuminate a white piece of paper, look through the column of liquid in the tube. Add solution until the black dot just disappears. This usually agrees pretty close with doing it in direct sunlight but is more consistant. If it is 50 that's a good number. I'd ignore the TA for now and test that later after you bring the FC down to maintenance level after you've gotten the CC down to zero. You're CA is low enough so keep using the cal-hypo.
Al