From my understanding and what searching I have done on the subject Payments Pro is only offered for the US, UK, and CA. Since Express Checkout is a part of the Payments Pro I assume the same goes for that as well.
It seems though if you are able to sign up for an Express Checkout for Germany that it should be supported there. I think the best thing to do would be to try implementing the Express Checkout with the credentials that you have obtained to see if it will work for you.
To do this you are already on the rite track. You should be running the checkout wizard and choose the Payments Pro US. This will include both the Direct Pay and Express Checkout options for you. You can continue through the wizard and generate the pages. After the pages are generated you can update the checkout page to remove the Direct Pay portion of the form and use only the Express Checkout. If the credentials you have are correct for this service then I think it should work for you.
If you get rid of the form on the checkout page you will essentially just remove the Direct Pay functionality. Please give this a try and let us know how far you get and what the result is.
