Will my age affect my chances of finding a funded PhD position?
The short answer is: no. Quite the contrary, many universities value the experience (preferably from industry) so it is beneficial. Also, your conference papers will be the most important factors in getting the PhD position and/or funding. I'd also emphasize that you should highlight the fact that you have a journal article (preferably A or A*) in progress.

I have not seen any such requirement which is restricting PhD or any academic degree to a specific age. In fact, doing so is illegal in most (read: all) European countries as it comes under age discrimination. 

To narrow it down further, different funding bodies could impose their own restrictions per project, for instance DAAD's grant that you mentioned is "to promote and fund young artists" according to them, that is why it is restricted to a certain age group. A similar example could be feminist studies where it could be restricted to a single gender. Again, this has nothing to do with general conditions of admission.