Hey, glad to help. Great progress.
Rimlights were a thing I just was gonna add to the edit. Beat me to it
Aside from what everyone else said, a few more cents with the time I have.
The shading looks alright. But like you said, looks plastic, so there are ways it could be improved.
Just basically replaced the colors, erased the 2 lightest colors and redrew those. Also added reflected lighting in the metal.
Added quick examples. Demonstrates overlap.
The shading you have (1) is a lot more similar to metal or plastic (2).
Meat/muscle is a lot darker/saturated like (3).
Realistically the texturing is different. Highlights are displaced by sinew, etc. to the point of being diffused (4).
That texturing you can just minimally suggest. But it's important that you do that kind of stuff, so we know that this monster guy is basically skinned.
Also, AA'd hand in the background?