RE: Dell Inspiron 7520 unable to install functional AMD video drivers
It sounds like you have been pretty thorough in troubleshooting the system, if you formatted / reinstalled Windows and have a clean driver installation and are still having the problem it sounds to me that there is a defect with the GPU / system board. If you eliminate software as the cause that leads only to hardware.
If you haven't tried disabling the wireless card (i admit it is a long shot, but one that can possibly save you having to replace the system board, for very little time or effort on your part) do so now and see if it helps, otherwise I am afraid that you are looking at a service. I wish that I have better news.
Specialize in Laptops, Mobile Devices