I agree with Hypnotic; maybe he liked the feeling of security that the palm tree gave him. Without the tree, he feels too exposed to go soak. Try adding a small plastic plant to one edge of the dish, or put the dish under some plants. That may make him feel secure enough to start soaking.

Nightcrawlers often act as stool softeners. That's the only reason I could think of for maybe cutting back on them, but I think quite a lot of people feed them as staples. It's a shame he refuses crickets; try to get him to eat them again, as variety in his diet is a good thing- maybe stop offering nightcrawlers for a bit and give crickets instead. He may get hungry enough just to eat the crickets haha.

I feed all my frogs in a separate container. I don't give them water, because they're not in there for a very long time, but I put very moist paper towelling down on the bottom so they get some moisture.

I don't know whether the nightcrawlers getting covered in Eco-Earth is a problem or not. Supposedly its fairly easy to pass, and with nightcrawlers as a staple it'll be even more so... I guess it just depends how much is getting into him. If its big chunks, or a large amount, that's more likely to be a problem than just a fine dusting on the outside of the worms.