No reason to only feed the adult males. Feed off large nymphs as much as you like. The numbers above suggest your colony will be able to support it just fine. If you started feeding off the adult females, you would have no producers and it couldn't sustain itself.
Feeding nymphs, some will be females, but because of the numbers you know you won't be feeding off more than you are producing, thus you will have new females maturing to replace the older ones.