@Halorser:
1. Start small. Like, fighter-sized. Bigger sprites take longer and can be frustrating at first.
2. If you want to build something bigger than a fighter, start big. Start with a big sprite, then shrink it down to your final size, when it's basically ready. It's easier to control brushes and suchlike when you're working on a large scale.
3. Start by blocking out the forms with light and darkness. Then block in color and finally add detail. That's usually the easiest way to get going when you're trying to build up your forms. It's much, much more difficult / time-consuming to do all this later, when it's pixel-sized and has tons of noisy detail making it hard to tell where up and down are.
The Endurance is great for early on. I think the main things I see not working are, largely:
A. Heavy blacklining that's too thick; it makes it look less than totally awesome. Don't feel bad, some of my early stuff here was hand-drawn stuff I scanned, and I had the same issues and worse, lol. It's hard to work that out; usually, the Right Answer is, when it's still large, work that down to a minimum as you do the lighting stage. At this point, you'd have to do a bunch of careful airbrush and other things to fix it.
B. As you've discovered the hard way, it's hard to get the lighting and overall sense of proportion right once you've committed to the details. The second attempt is actually very nice in a lot of ways, but a few more stages will get it to excellent.
A better way to block things out is to get your shapes, core details and lighting filled in with grays, then use that with one or more layers to build your basic colors. Generally, if you're working at a large scale, you can just do the whole thing with a few layers.