Are you accidentally pressing shift + numbe or shift + mousewheel?
Try rebinding your spells.
Check the profiles section in /dominos
No, you can't keep the original UI with Dominos. But, the primary action bar does change on shift + number/mousewheel by default.
Eventually. When reviewing the code changes between 7.2 and 7.3, I didn't notice anything major that needs changing.
Have you tried reinstalling the addon (without resetting things :P)
I'm not sure, but its not something I'm specifically doing.
That usually indicates an addon conflict to me. Try with just Dominos + Dominos_Config enabled on that character.
Each spec starts out with its own set of buttons (at least that's how the Blizzard UI does it, which Dominos mirrors).
You can have more bars, but not more than 120 buttons. To change the number of bars per button do:
/dom numbars number
Where number is a value between 1 and 120. This will reset your bar positions in a way that's not super great right now.