Thru the roof as in high ph/alkalinity? If so, I'd dump in half a gallon of muriatic acid and run the pool all day, then test again (repeating if necessary). You can get fancy "ph reducers" but muriatic acid will work just fine, and is very cheap. Oh, and the test strip
are fairly accurate, but if you are still in doubt take a sample to Paddock. They will run a computer analysis on it for free.
How much DE did you use, and where did you put it? Most folks here only use that when they are back-flushing (once a month, or if your pressures start to rise). You pour it right in the filter trap. Also, do not go swimming for at least 24 hours after you shock it.
How long are you running the pump? On that pool, I'd say you need to be running it at least 8 hours a day (especially in the summer). If you are on the APS saver plan, run it at night to save on the electric bill.
Also, for your chlorine tabs, you might want to consider the ones from Paddock. They are a bit more expensive, but have stabilizers so the chlorine doesn't boil off immediately. Also, another trick is to leave them in the plastic package, but with one side slit open. This makes them last a bit longer.
I'm no expert as you know, so grain of salt, YMMV, yadda yadda.
