Thank you for your post!
Testing and Development is aware of this issue. I will add your information and thread to the original report. You might see the suggestion mentioned on Re: FileMaker Pro 15 and High-DPI Screen Problems in Windows
More problems with Microsoft surfacebook-- seems like fields do not render properly. This is evidence of the problem. When I develop, seems like filemaker does not render images and fonts properly. This is a big problem for a dual platform database development tool. Any suggestions would be appreciated. I have tried scaling with no results.
The issue with pop-up menus and drop-down lists always displaying at 100% has been addressed in FileMaker Pro 16.