Hi
Being the 'Mature one' (see reply from freerunner) is not easy. Well done to you for moving on & taking the plunge with your second wife - also sounds like you have really made an effort with your daughter to keep up the relationship.
Your tax code should be the same paying maintenance - think it might only change if you are behind on payments & they are trying to collect back-maintenance from you directly. But from what you have said, sounds like you are keeping up with the payments...it is tough going though. I am still learning to communicate with my ex, it sometimes seems easier to argue but mostly we are just covering old ground. I am working to stay clear of topics that might lead to a disagreement.
Someone told me that car conversations are great for teenagers - they don't have to look at you while discussing tricky subjects, they also can't run away so they are a bit of a captive audience...might be useful for the years to come?