No more trichlor for this pool. Trichlor is stabilized and will continue to add CYA to your water which you don't want. It is already a little high at 70. Take a look at the Best Guess table in my signature for the correlation between CYA and needed chlorine levels. I'd just stick with bleach for your pool. In this size pool, each quart of 6% bleach will add about 1/2ppm of chlorine. You'll need to test and add bleach every evening or two. You'll soon learn how your pool behaves. Add enough bleach to take your cl level back up to 10. Tomorrow evening, test again and see what chlorine level you have. You want to make sure you keep it between 5-10 all the time. You may find that with a CYA of 70, you'll only need to add bleach every 2nd or 3rd day. You'll find your pools pattern after a few days of testing. Don't let it drop below 5pm or you risk an algae bloom.

You also probably want to lower your pH a bit. Add a cup of muriatic acid slowly in front of a return jet. Don't splash it on you or the liner and stay upwind of the fumes. Wear gloves and glasses. It is nasty stuff. Test pH several hours later and see how much that lowered the pH. Don't test pH when your chlorine is high, however or you'll get an inaccurate reading. Test it in the evening before you add more bleach. If it is still a little high, repeat the dose.