Just a thought for a fleet that has vader and avenger. If you make an attack with avenger (not adding any avenger dice) spend a red token to get re rolls via vader, can you then add the extra Dice to the attack, I would say yes as they both modify dice and so happen at the same time.
You got some names wrong but yes. You can spend the token, add the die, then reroll of you want to.
The real issue is that this is a really inefficient way to trigger Devastator. It requires that you either have a double arc or two targets with gunnery teams, in both cases this is going to telegraph your plan to your opponent and allow them to take actions in response.
It's my pain meds....lots of head confusion.