Hello and Welcome to TFP!
For a CYA of 60-80, the shock level to get ahead of the algae is 24-31ppm of chlorine! Much less than that and the algae will find life uncomfortable, but will still multiply and your pool will never clear up. The algaecide is like a bandaid for a kid. It doesn't really do anything except make you feel better. Algaecide doesn't really kill anything and at this point is to little to late.
The only way to test at the high FC levels you need is with a drop based kit.
You may also find the pool cleaning and future maintenance easier if you get the CYA down to the 20/30/40 range.
Bleach is the method we recommend to use to get the chlorine in the pool.
What is your pH? The low end (7.2) is best for this process. But you have to test pH when FC is less than 10ppm
While cleaning your pool, you can ignore and not test for TA and CH.
Backwash when the pressure goes up 25% above clean pressure. You don't need new sand as it doesn't wear out. Your major issue at this point is lack of sufficient chlorine.
Up at the top of the page is PoolMath. Go to that page and familiarize yourself with it. It will calculate the amount of chemicals you need.
Go to Pool School also and read up.
If you take some time to read and ask some questions, you will be able to learn what it takes clean up that pool in no time.