I have been told the ABD actually gives out some interest based on how many bells you put in, but it's not every day. What % of interest do I get and how do I claim it? Do I have to play every day for it to count or what?
According to this wiki:
On the first day of the month, you receive interest on your Savings at the rate of 0.5% per month, subject to a maximum interest of 99,999 bells.
So you do not get interest until the month change.