Way back in the early 1980's, I was a communications consultant for a small company that put mini-computers in banks to do their processing. I looked at the Brothers typewriters to print output from computer terminals. A company produced a kit to add a serial interface to the typewriter. Worked very well. All the paper and print head movements were controllable, just as you found.
I have no clue if there is any documentation on-line for the interface.
Paul