Reference:http://i.imgur.com/3ZHWfLE.jpg

Still working on this.  Trying to bring him closer to the real thing.  Not worrying so much about detailing until I have the proportions and form down.
Mostly focused on the shape of the eyes, nose, and mouth still.  Positioning of them as well.
Brought the shape of the head less outward as it descends.

Yes.
The jpeg compressed the image.
You can't recover what was lost when you saved it that way.
The png will save at the jpeg's quality.  It's not a 2-way street.
You are effectively working on a blurry image now.

So, the more I find myself working on art in general the more I find myself staring at a monitor all day.  I've gone through my settings to adjust everything to prevent so much white and bright colors on my windows.  But it only helps when I'm moving through them.  Not specifically art itself.

I learned long ago to avoid backgrounds that are too bright or too dark while you work on a piece because it can inhibit your color choices and detract from your sense of how well a sprite/object/whathaveyou actually reads.

Has anyone spent some real time focusing on finding that sort of optimum color for working on art for extended periods of time.  A color that just seems to work best for both art and not stressing your eyes?

My first thoughts would be that grey or green would probably be best and I often use a sort of middle saturation level green unless I'm working on coloring something green.

Any thoughts?  Im a bit over-sensitive to yellow tones for some reason.

I don't mean to sound like a dick, but I asked about my car and you offered advice about my boat, my house, and my girlfriends attitude.

It's really hard for me to do form, color, and shade one piece and then do another piece and make them match.

To complete your analogy, you asked about your life and then focused on your car.  I pointed out that you had more than the car to worry about and gave you pointers one what to do about the entire set of problems.
This all comes from practice and is why I mention that you should work on one small piece until you have a firmer grasp of form, color, and shading and then extend your piece or work on a large piece from there.
Ideally you wouldn't begin with such a large composition and you would focus on the fundamentals that are required to accomplish your goal rather than trying to get it to look right first and then backwards working your way towards securing those fundamentals.

I started out this way.  Took a lot of work and rework to learn that I should discard some of my ideas about how to go about creating a piece and adopt new ones even if they seemed really difficult.  Most of the things one tries in the beginning are actually bad for your art and the process of making it.  In the end it's all about practice practice practice though so keep going.

I really recommend that you work on a small portion of it and then move forward.
For knee and hip joints in robots look online at big robots.  Zords from power rangers, Transformers, and Gundams all have this sort of blocky shape to them.  They would be good examples of things to try.