If your fish get fat your over feeding them!

Seriously tho... I also have Angelfish and I can say that they are indeed piggies! When they see you anywhere near the glass they come a running as if they havent eaten in days~
If you are really only giving them a few flakes throughout the day that is fine IMO. It keeps them happy!

The brine shrimp in the evening is fine too, at least it is with my guys and they have been growing fast and strong for a little over 7 months.
I think you are doing fine and the water change is ideal, again IMO... that is what I do also. I also vacuum the bottom of the tank to pick up any uneaten food before it can change the water readings.
Good luck with your babies.. sounds like they are very happy lil campers!

~ kate