Unfortunately, pixel art is, as the words say, an art, so there is nothing like a tutorial that can cover it and turn anyone into a master. It's an art because it requires knowledge of the art of drawing and the technique of managing pixels and small palettes.
That said, if you are seriously motivated, nothing can stop you from learning ;)
The best place where to go is http://pixelation.org/ - read as much as possible, understand the philosophy of the place, learn about the terminology and the concepts, watch the videos, do a lot of practice, and use the critique/help of the geniuses over there to improve.
I'm working on a new version of my game, I decided to try using a view/camera system like yours
but using the mouse (moving the mouse left and right rotates what you see, like in BOH using arrows)
Something I noticed is for any movement that is not round (a number with decimals, like 1.235),
it causes problems. It causes the screen and the player to 'shake' or 'jitter' a bit
Your game is at a much lower resolution to work on older system, so it must have been even harder making sure
everything looks perfect like it does.
What I did was to use trigonometry so that no matter what the angle is, the player moves the same distance.
But at an angle, this is what causes the decimals and the jittering
In your game movement is super smooth, it's fantastic, the screen doesn't jitter and the character doesn't jitter either. If you don't mind me asking, how did you handle movement at an angle?
I simply rotate the background with the source center being the position of the character controlled by the player and the destination center being the center of the screen. The character itself is drawn after the rotation, always at the same position (i.e. the center of the screen).