I have almost the same setup, except I have a newer i7, and an XFX 390. and 24GB ram, but that shouldn't matter for this game. I used the have the same problems as you, 10-25 FPS, dropping frames like mad, unless I was indoors or in the starter area. It started working for me since I have been on Windows 10, my catalyst…
Ethical? As in you don't own 7, can't upgrade and want to reap the enhanced performance of Vulkan/DX12 ? I highly doubt they will re-write the entire game to use Vulkan, they may not even upgrade it to DX12, as reaping the benefits of that would require a complete re-write as well.