Maybe he is getting some crickets, but poor appetite isn't the greatest sign in a white's. Neither is the not climbing. Do you use a powdered calcium supplement? That can help prevent MBD.
I might be hesitant to give him wax worms unless he'd lost a significant amount of weight. They aren't very nutritious, and some frogs refuse to eat anything else after being given them. They're like frog donuts. Still, with some vitamin powder, they might not be a bad idea if the frog starts eating even less.

I think there are reptile appetite stimulants if it comes to that. I've heard a bath in water with a drop of honey as something that will help improve appetite. Or a bath in water with unflavored pedialyte to restore electrolytes if the frog has been starving but I can't say whether that would work for that purpose and it does run the danger of stressing the frog out further. I'd only keep it in mind as a last resort.

As far as humidity, White's are pretty tolerant of a broad spectrum according to the wide range of recommendations I've read in care sheets, though Limabean's right that apparently they do fine in low humidity and high humidity raises the risk of bacteria breeding in the tank. However, as long as there's sufficient ventilation in the tank I wouldn't worry about higher humidity.