Alright then, questions are good, they mean you are willing to learn!
For the crickets, you feed him crickets that are no bigger than his head, any bigger and the frog could choke trying. You could try feeding say four at a time every two or three days (I feed my two adults every three days, about four crickets each).
As for dusting, once a week is more than enough, your frog is big enough, he doesn't need it every day.
You don't have to feed him mice, your right. they are very high in fat content and really he is too small. If you want to feed him pinky mice later on, its your call, but they don't need to be in your frogs diet.
as for Earthworm, you need to make sure that wherever they are collected isn't sprayed with pesticide (even in say, your backyard, if your neighboor uses pesticide, then you should pick somewhere safer) and cut them into pieces that will suit your frogs size. Mealworms and waxworms are great, again watch the size, and don't offer them every feeding, since the worms are fatty too. Crickets should be your main staple. You can of course offer say one a feeding with three or so crickets.
Freeze dried stuff could be a waste of time, then again, it could be worth your money. Because WTF hunt live food, he may not be willing to eat something that isn't moving. This said, I've got one frogs that love the feeding bowl and eats just about anything that drops in there, literally. I haven't tried freeze dried stuff, but I know that some use it and their frogs eat it, and some don't because their frogs refuse to touch it. You could try, never hurts, but your frog may never be interested in it.
Ok, waterfall wise, I have one, the frogs love it. (I broke a piece yesterday and they were really confused as to where it had gone!) You need to clean it at least twice a week, more if you can, but they are good sources of water. If you can find the... I can never remember the name, but its like a repti-hammock, but with a water dish in the middle, that would solve your space problem, since you hang it on the glass instead of on the bottom of the tank. I have two, I love them! (but I also have a huge tank, so I can't acutally touch the bottom without a chair, so they are also convinient) but you don't actually need to add a water dish if you keep the fountain clean. You may have to go on the preference of your frog too, he may like to soak in the water dish, so maybe try both and see which he prefers? up to you.
Anyways, I hope this helps. I could write a book on my opinion!
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I think my frog owns a megaphone....
