Nikki I just finished looking at your pictures and I have to to say that scab does look bad. I would treat it with just a little neosporin for a couple days and see if that helps it heal and get rid of bacteria. Hopefully by now you've lowered humidity. Unfortunately you cannot always trust the people in the pet stores, they may look intelligent and speak nice but 9 times out of 10 they have no idea what they're talking about. The people in my local pet store keep large turtles in cages that are small to the point where the turtle can't even turn around, this is just one example of the cruelty they're capable of.

If you've lowered humidity I'd say your next step is grabbing some plants like Cheri has suggested. These will make him feel safer and more secure, since he is wild caught, this will probably calm him down significantly. Another thing you can do is tape pieces of paper to the outside sides of the tank to keep him from seeing out for the first few weeks. This will reduce stress substantially. I have done this will all my frogs but the very first one, Ginger here gave me the idea after I had already had my first frog for a while. So far it has worked to great success, it makes the frogs feel safer and keeps you from spying on them all the time, which trust me is fun, but it can lead more stress can lead to serious health problems. Fake plants are fine, just make sure they're big enough that he can stand on them without tipping them over, Exo Terra makes good ones. I use a fake Exo Terra fern in my ten gallon for my baby WTF and he seems to enjoy it. Also maybe some more hanging plants will help him to feel safer as well. Just provide more places for him to hide and he should stop trying to escape.

I'm sure if you posted a picture of the poop no one would get grossed out, but unless the signs of parasites or other illnesses are obvious, I don't think we'll be able to tell much from a picture.