We don't recommend teststrips because they aren't very accurate. Most of us use the kit that Ben sells at the sister site to this forum www.poolsolutions.com. It WILL test high cl levels which you're going to need to be able to do if you decide to keep your cya of 100. At the very least, buy the 5-way drops based kit at Walmart for about $15. It won't test cl higher than 5, but you can dilute the sample and make it test higher. However, just be aware that with each dilution, you do lose some accuracy. To dilute - take one part pool water and two parts distilled water, mix them together and then test as usual. Then multiply the result by 3. (If it were my pool, I'd do the partial drain and lower cya to 50. Just my opinion.)

About the dog - dogs swim in green ponds all the time so............. but, I probably wouldn't let it swim in the pool when it had been shocked so high.

Hope this helps. Keep us posted how things are going.