Edit: Sorry. I made these comments thinking it was the HIGH sierra thread.
@BanjoBobby - I think mine was pretty much rock solid on High Sierra but I was using a different graphics card.
FCPX - is it generally stable for others in the version you have?
OSX seems to crash on hardware glitches more tahn windows, but if it is stable in windows you can be 'fairly' sure its not a hardware issue.
Dual booting can bring its own complications (sometimes relating to NVRAM) but if you have followed a guide, that's probably been covered.
If you are up for a complete rebuild, you might want to look at -
https://www.tonymacx86.com/threads/...p-6300-pro-using-clover-uefi-hotpatch.265384/ - signs are that it's a better build and not that much more difficult a process.
but a q for you - Why no ssd?