i feed mine frozen blood worms. from what i gather, they won't eat flakes and freeze-dried foods can cause health problems.
i'm not entirely sure how to go about sexing them, i've read up on it but looking at my frogs, i really cannot tell.
what kind of tank setup do you have?
I feed my ADFs live blackworms and tubifex worms. Sometimes I also give them a tiny pellet called Frog and Tadpole Bites, which is made by HBH.
They are mature at around a year of age and at that time the male will have a white bump just behind it's underarms. Males are usually smaller than females too.