Feeding: just give them as many flies/moths/dragonflies/etc. as they can handle.. if there is still any live food left in the cage after an hour, then she is well fed enough! I have mated all mine on the day they became two weeks as adults (the males are anywhere from 3-5 weeks old - it seems in my experience the male is the key, the older the better, females will mate earlier than two weeks even).
These aren't the greatest pics, had to shoot them on the fly - the male wasted no time in getting on my second-to-last unmated female this morning.
The male will remain on the female a long, long time - sometimes days, and one of my males actually dropped off, dead, after five days. He didn't eat and wouldn't even drink drops of honey stuck to his claws. Poor fellow.. but that's normal for them maybe?
At any rate the male will drum the female's wings with his forelegs and even a female who is actively eating other stuff doesn't seem to pose any threat to the male - until he jumps off her back. The drumming seems to me to be something saying 'I am still here, don't eat me!' but once she doesn't get that stimulus, he is fair game! Get the male out of the cage the instant he leaves her - but in the meantime, he may remate her up to four times in a day or two, so I would let him stay on as long as he chooses to - maybe better ensures fertilization.