1. The only way that I have figured out how to change the decimals is to change the hardcoded value that is currently 2 in the get_decimal_places of coin-adapter-turtlecoin.php
2. The fact that I can change this and the decimals do change, should say that this is where the app is getting the decimal value from… not the coin.csv (if I change, it does nothing). Not the wallets_turtle_coins_filter… if I add it does nothing.
The only way to get the correct value is change the hardcoded value of get_decimal_places method. I think your code might have a bug in it, have you fully tested with 2ACoin?