how long can I be flagged for a chapter 14-12(c)?

The Chapter can stay open until such time as the deficiency has been corrected and no trace of repeat offense. Or until such time as your Chapter is complete and you are no longer in the service. So, in essence, there is no way for anyone other than your CoC to predict how long your Flag will stay in place. And if they aren't telling you, then you should take that hint that it will not be any time soon.

What you need to focus on is getting your cranium extracted from your fourth point of contact, straighten up and fly right. Don't pester your Leadership about your Flag. Do your job and stay out of trouble. As long as you do what you are supposed to do, at some point you will be called in to be notified that your Flag has been lifted.

And that is if you will not be Chaptered out of the Army.

You’ll stay flagged until you’re separated. In fact, you can be flagged for separation and have the separation suspended and stay flagged for an additional year.

Have you addressed your concern with you Command? It’ll be a while. It’s just like a relationship, when you destroy the trust one have in you, it takes a while to rebuild.