Hmm,
Not sure if I have too much else to add at this point, the edit you did on the big version is definitely an improvement.
The small version could use some clean-up here and there. The color range exercise is a good one, personally I like things with high contrast.
Being self taught is hard, you need to be able to judge yourself as hard as you can and as accurate as you can. I'm self taught too, and from my experience, the key for improving is to absorb as much information as you can from people who is further on the learning curve and practice right away. I do really recommend watching Marco Bucci, Modern Day James, Proko or similar channels on YouTube (Again, I can't stress this enough, the more you learn things not related to pixel art the fastest your progress at pixel art will be. The improvement is 10 times faster than if you learn with only pixel art).
I think a topic you may find useful for improving is Value, color often masks our mistakes, so working only in black and white (AKA Value Only) at least for a bit should make it easier for you to spot what you can improve. If it reads good in black and white, color is just a pinch of salt on top.
Here's a work I did a couple weeks ago as an example, that although not great, things have a good readability both on color and on black and white (Value Only)
Here's the last edit you did with the same treatment. Shapes loose a bit of readability don't you think? For example, the leg and arm on the far side look closer than the leg and arm on the closest side.
A last piece of advice to close is squint your eyes as much and as often as you can when drawing, If things are readable doing this, they will be crystal clear when not doing it.
Hope this helps a bit!