Confusing Ph vs TA

You need to do nothing!!!!
Just manage your pH, wait until it gets above 8 (purple hues), then lower to 7.2...pH will rise on it's own. When you lower pH with muriatic acid, you lower TA.
When your TA gets to 60-80, STOP lower pH so low, and it should be fairly stable between 7.8 and 8. Again, don't lower until you get purple hues, and with TA of 60-80, only lower to 7.8.
 
Do nothing.
Your pH will rise, and when it gets above 8, add some acid to bring it down into the 7's
The acid will also slowly (slower than it effects pH) bring down the TA. Once your TA is ~70, the need for acid will be minimal. Don't go crazy with acid to try to knock down the TA faster - it will crash your pH, which would be very bad.

Some do try to accelerate the process a little, by dropping the pH to 7.2, and repeating when above 8, until the TA comes into range. While just doing normal adds will take longer, in the end the amount of acid used will be the same. No harm to that, and no risk of going too low.