(I didn't see Ep02-15 yet...)
Locke freaks out only when his newfound confidence in his abilities, and knowledge is shaken. This confidence is only based on his ability to walk. He was not denied the walkabout, he is doing it.
Locke's turning point was not when he saw the "monster". He said(to Jack I think or Charlie) "I stared into the eye of this island. And it was beautiful".
Locke's turning point is when he was losing his legs again. Then Boone died. To him, the Island was telling him that without his legs, he is nothing and this can be taken away just as easily as it was given to him. Suddenly, Locke doesn't feel so hot anymore and he questions everything again.
He was also the best woodsman around, before the "ninjas" showed up. And as the "losties" are getting more familiar with their environment, his uniqueness is fading, as everyone is catching up to his skills and he is slowly but surely becoming "like everyone else". IMO.
By the way, we still don't know how he lost his legs in the first place.