First of all, I have to say this is pretty good. You seem to be very worried about keeping certain details readable, although you have to understand, when you make something this small, details will be lost. For example, in the ref, his foot has small indent, but in your version, it looks way too big! Just ignore the dent when you draw it, or suggest a hole by simply using a darker color. Also, the green highlight doesn't really read as a second light source, it just looks like an ugly outline. You could easily remove it. And the one on the left looks much better, even though you can't see his eyes. When I look at him, I instantly see it as Iron Man, you don't need all the little details for me to get that.

And just to reiterate, you have a pretty good sense of anatomy, and you captured the image well.