Enforce Balk or not

[Gorkes]

I got into a funny situation last weekend and I'm not sure if I did the right thing:
There was R2.
Now the pitcher balks (no stop) and R2 steals 3rd.
The balk is called, but the batter tries to hit the ball even so.
On the swing, there's a catcher's interference.

What did I do:
I placed the batter on 1st for interference and R2 on 3rd, because he was stealing the base (didn't find that part in the rules (yet) , but I thought when a runner is stealing and the catcher interferes, the runner can advance, if he's not stealing he stays unless forced to advance).
Of course now the coach comes out to argue, saying that it was a balk and therefore R2 gets to 3rd but batter goes back to bat.
I explain him my decision and that because Batter got to 1st and R2 advanced a base, I did not enforce the balk that was called earlier on the play.

What is the correct ruling?
- R2 to 3rd and batter to 1st
- batter to 1st, R2 stays
- R2 to 3rd, batter back to the box
-> beacause R2 stayed, the balk is enforced

thx for ur help