Thanks for clarifying that - she is being totally unreasonable.
I commend you for dealing with your kids the way you are. They will grow up (if they haven't already) to have the utmost respect for you. It's a shame that she is being so petty and bad-mouthing you to the children. You will always be their dad and they will love you for that.
I think that you are truly being the adult in this situation and she is acting like an angry, unruly child. Do you have any fear that she will cause problems when you move to the same town? If so, do you have a support system in place to keep you grounded?
Finally, it bears repeating - you are NOT being selfish. Cudos to you for thinking of your son and being there to support him while he finishes school. You are truly a good parent.
There are no unresolved issues - they just didn't resolve themselves the way we would have liked. "Grinder and Bandler - Neuro-Linguistic Programming"