My muscle size and strength is unbalanced. My biceps is bigger than I expected after two years of training, but it looks too round, thin, and hump-like. The space between it and my forearm doesn't look very muscular at all. I've tried using several different techniques, but I've been stuck like this for a long time.

My forearms are weirdly shaped as well. When my hand is facing downwards, it looks great, almost like Popeye's arms. I've been complimented since I was a kid because of it. When my hand is turned upward, it looks very thin. The sides of my forearm are unspectacular in any case.

Even my shoulders are unbalanced. The top is great, but when I let my arms rest they don't look as wide or thick as I want them to be.

What could I be doing wrong, and how can I do better?
PS. Is it possible to get a stronger grip using dumbbells?