Misty could be a bit of an asshole at times but I don't think I remember anybody calling her a psychopath.
Also that scene with Gou making an evil face is probably being played for laughs, I doubt it means anything, he's just annoyed he didn't catch Dewgong on the first shot I am assuming.
Probably, but still. Let's see what his reactions to later difficult captures is. If it's something like what happened in today's episodes, those who think he's a psychopath may be on to something. It would actually make an interesting story if he does go down a darker path like that in his capture goal.