That looks promising!
I thought the big long thing on him was like the tail on a slug and was behind him. Maybe I'm wrong on that?
My first suggestion is to respline the mouth corner so it is not an actual corner but a U-turn instead. You can quickly terminate the new spline (highlighted) with a hook.
If the mouth opening is one continuous loop it is easy to extrude it inward when you want to make the inside of the mouth.
The part I circled in orange has a dead end spline. That will want to be fixed with some combination of five-pointers and hooks.
I have a video about one user's dead end spline. It's not exactly the same situation but it might be helpful...
https://forums.hash.com/topic/42423-exercise-11-geeeeraff/?do=findComment&comment=372103