Yes, this is what I meant, just shorthand - the fact that the the rotary spins 1 full revolution when commanded to do so suggests that the board is configured and operating properly.
No, the steps are correct as they are, see above regarding making the full revolution.
In the “full circumference rectangle” example, if you have just that rectangle in your job (or set anything else in the LB job to not output so only the rectangle is being output), then save the gCode, we can take a look at that here. We want to find the long line that goes around, and see what the coordinates that A is commanded to. If you upload that file and give me a link here, I can take a look. That A values should be just around 360 degrees.
The simple solution is to just scale your “Y” dimension in your designs up by a factor that gets you a full revolution and see if that is consistent/ repeatable.
As far as the stepper motor skipping, if you upload a video with audio of running said job, I can tell you if it is happening and it might help spot if there are any other issues.
For reference on object weight, I spin a full wine bottle on each rotary as a test.