I'm a little confused by two of your rulings...
Regarding the having no models on the table ending the game. Your ruling actually makes it easier for a tabled army to win, instead of punishing them, which I feel like your intention was.
Regarding the Balewind Vortex, I'm not sure why you think that they cannot be targeted by spells or ranged attacks? They can still be attacked as normal, similarly, if you are up on the Vortex, you're probably not going to be close enough to score the objective anyhow.