About the sad walk. He definitely looks sad, given the hunched over body and facial features, and from a technical point of view, the animation is very well done! But. There is something in the movement that's slightly odd, some sections that stray away from sad.
Overall he feels almost too smooth. If I look at the body/head section in the front view, it's super smooth, where you don't feel like he's taking steps, you don't feel the impact of the body after each step. I think there's also too much countering hip and body action. That's only in the front view though.
In the sideview the arms feel too overlappy. It's mostly the wrist that has too much drag and overlap, so I would take most of that out.
Another thing that feels weird is that while the body is super smooth and slow, the legs feel too fast. It's a weird contrast to have them that fast while the rest of the body is so slow and smooth. It's not that you can't have someone walk fast while being sad, it's not that, but if I look just at the upper part he feels slow, when I look just at the legs, he feels fast. So I think that if you slow down the legs, it will just push the feeling of sad/disappointed more.
Hope that helps!