Which link isn't working for you?

Your pump and filter seem to be a pretty good size match.

Good decision to order the good kit. Two things I want you to try. Shock your pool up a little higher. With a CYA of 40, shock level would be 15ppm. Go ahead and take the chlorine up to that level and let's see if that makes any difference for you.

Also, can you let a reputable pool store test your CC and calcium hardness for you and post the results. You're probably right that the calcium isn't high by looking at the info you posted above, but let's just double check it to be sure. Plus, since it is a plaster pool, you really need to know the reading.

Actually, one last thing to do. This evening, test the chlorine after the sun is off the pool. Add enough bleach to get back to chlorine level of 15ppm. An hour or two later, test the chlorine again. Then, in the morning within two hours of sunrise, test the chlorine again. I'm trying to determine if you are losing chlorine overnight. When you lose more than 1ppm of chlorine overnight, that tells us you are fighting something in the water.

Your OTO kit isn't going to test cl levels higher than 5ppm. Until you get your good kit, you can force your kt to read higher with a dilution method described below. Each dilution does lose some accuracy, but it is better than nothing for now.

Testing Without a Good Kit

(A gallon should add about 3ppm of chlorine to a 21K pool.)

Run your pump 24/7 while you are trying to clear a pool.