Should I leave my PhD in year 6 or just take a bit of a leave and try to regroup?/ What is an "appropriate" level of angst to go through with a PhD?
I have just completed my PhD, so the angst you speak of is still fresh in my memory.  I will say that it is good that you are thinking about your options instead of making a rash decision.  We can not answer whether or not you should leave your PhD, that decision is yours and yours alone to make.

Having said that, a few things to consider (some of which you have alluded to already):


Your enjoyment of the research topic - is it stronger than the frustration hat you feel?  You mention that the move between schools and the internal politics has had a negative effect on your research productivity, reflect on what is causing that.
Your career goals have shifted, so is the PhD relevant to what you are planning to do?  More so, is the PhD in any way holding you back from achieving the career goals?
An important question with regards to your PhD, is what is it leading to?  What is the 'end game' of it all, so to speak?
Will taking a year off having a negative effect on your funding etc? Conversely, will the year off allow you to, as you say, regroup - and also perhaps explore that career path.


I am 36, and just finished my PhD - so your age is not that important, you're still young.  Never feel that you are 'obliged' to complete the PhD in a certain time frame, if at all - you have to look out for what is best for you.