Thank you for your question
My name is ***** ***** I shall do my best to help you
It is up to your ex whether she applies to the German courts and then enforces their Order in the UK or she goes directly to the Uk courts.
if she goes to the UK courts they will follow the CMS guidelines and you will be Ordered to pay 16% of 86% of your gross income - so £688 a month at most.
In either country you will be able to request a DNA test
Please ask if you need further details
My apologies for the delay
1. Yes you would be assessed under the German system
2. Correct - that is why it is 86% of your income not 100%
3. The fact that the two systems do not match is not a ground for contesting the calculation. The German system is based on set rates - you can find a link here
You were never married so spouse maintenance was never an issue - I gave that link to take you to the latest child maintenance tables - my saved link was to the old one
If your ex choses to apply in Germany you will pay under the Dusseldorf tables.
The fact that you would pay less if it was assessed in the Uk is not relevant - and none of the arguments that you mention relate to child maintenance
I have only dealt with Child Maintenance - since she chose to up and go to Germany she has no chance of a successful CHildren Act applictaion in the UK regarding her housing needs - you simply do not earn enough.