So...you added elbows? The typology is what needs most of the love at this point. Here is an example of how the typology should look like. Its by Gary Newman Its relatively low poly, but it shows were the polygons need to be and were they dont need to be.
I second the relax. Also, the most tricky part when doing any type of deformation is in the shoulder area. You really want to have loops running around that area right all the way up as far as you can. So instead of merging the loops at the shoulder, have the flow up and over the shoulder to the back. This way, you can get…
well, moving a vert that's constrained to edges means that you can straighten and work to better evenly distribute your edges around your forms without drastically changing the shape of the forms. the blue line is how you want your edges to be, make them smooth curves and lines. this makes unwrapping it cleaner/easier and…