He can probably eat 4-5 week old crickets, but I wouldn't try fully grown ones just yet. The general rule with feeder size is that the width of insect should be smaller than space between the cham's eyes. That's basically the size of their mouth... Think of it this way; if you cut too big a size off your steak, and then have troubles getting it all down. You can choke on it, or have some go down your wind pipe trying to manage it.
With males you don't have to worry about cutting back and restricting their diets, as young as the females. You can feed him as much as he can eat everyday day up until 7-10 months. Each cham is different; but a good indication is that he should have all his big boy colors popping, and he'll look more muscular. Sometimes they'll instinctively start eating less and less. Once he's grown it's recommended to feed 3 - 5 of the large feeders every 3 days.