Stay focused on what you want to happen from here on. Spending time going over what’s already happened probably won’t help. It may be necessary to compromise on some things, but you need to be clear about what you won’t compromise on, and clearly and calmly explain why.
Try to maintain a focus on positive, workable solutions. It’s often a good idea to summarize and share what you’ve agreed in writing with your ex- and with your teenager so everyone is clear.
Don’t be afraid to ask for some professional help (ideally, sooner rather than later) in dealing with communication with either your ex- or your teenager. It doesn’t have to be labeled ‘counselling’ if that’s likely to be met with resistance. Think of it more like you would a work training course, designed to help build everyone’s skills.
With your teenager’s welfare in the center of the discussion, and possibly with professional help, you can work out where you’re able to compromise, and where you may have to simply accept the fact that not everything can be in your control.