Males can usually be visually sexed as early 10 weeks old or so, however, it may take longer to see their bulges and pre-anal pores on some males..so i would say you could successfully sex a fatty at around 3 months or so when it weighs around 15 grams or so..
If you see pre-anal pores and 2 bulges then you have a boy, if not the you have a girl
It's a nice light normal. Nearly all my fatties I hatched from normal parents for the past 2 seasons are that light. I don't know for sure whether or not either parent is het for albino, but it's highly unlikely that all the babies aren't het for albino.