I would say your best bet is to do a fresh install of your previous version of windows 10 and there is a registry entry where you tell the machine to get its updates from a local wsus server rather than microsoft update. If you set this address to a random one on your network windows won't be able to get any updates and should keep you on Windows 10 (1703 or whatever it was) until YOU decide that you want to do updates.

I am going to do this over the weekend as I'm having exactly the same problems as yourself and it is so frustrating to have the lower hashrates and the crashing every day.