I'm starting work on this project now for my house. I have about 10 blinds I want to control all similar to the ones you have. Do you find those tiny stepper motors have enough grunt to reliably control those blinds?
It can't close the blinds as tightly as the manual worm gear mechanism, but I find it does well enough. If I ran across a cheap worm gear actuator that was small enough to fit in a 2" rail, I'd probably give it a try. One thing you could try first is to convert the 28BYJ motors into a bipolar motor. There are some instructions for how to do that here:
http://www.jangeox.be/2013/10/change-unipolar-28byj-48-to-bipolar.html. The author there claims about double the torque after this modification.
For my issue (closing the blinds tighter), I don't think it will work, because the 'braking' force of the motor when at rest would not change. The worm gear excels at this by providing a mechanical solution.
I was loosing steps on my initial test, but I could have speed and acceleration values incorrect. Unless I'm missing something and this is probably a dumb newbie question. I see you have posted a library, but I don't see an .INO file. How do I use your library?
I'm using platformio instead of the (shitty) Arduino IDE. Just put the Node and RFM69_WL checkouts into ~/.platformio/lib if you are on Mac/Linux. No idea on Windows, but there will be some documented path for platformio libs to go.