Since it's been so long since he's eaten you might want to try to force feed so that the food actually gets in his mouth. Instead of crickets try cut up night crawlers. They're softer and easier to get in the mouth. Or even wax worms would be okay for now since he hasn't eaten so the extra fat would be okay. This is very stressful for the frog so it's only done when completely necessary. You just need something blunt and flat (I've used a rounded cuticle pusher that wasn't sharp) to separate he mouth and then just push the food in so they have to swallow it. In your case it sounds like it might be somewhat welcome since he seems to actually want to eat.