Ye Zun always looks so nicely deranged! :D
He does! He's an adorable danger specter with cute teeth.

I need to watch that again, that scene never made sense to me! I mean, what had the guy even done. And what's the purpose of that scar? It would make a lot of sense if this was crazy editing after the fact - not that we don't still have to find a way to fit it into canon... Maybe bad choices made at the start of Envoy-ing, like you suggest.
Shen Wei did see an ex-palace guard murder the head of the palace guards, so yeah, it does make sense that he'd do something, but ... the dramatic scar was kinda pointless. Especially since he didn't even imprison Zhu Jiu.