This may be a dumb comment since I haven’t read the whole thread but why aren’t you using vmware fusion to run windows. It has a few quirks, but nothing like what you describe and its speed is quite good. On my 2-monitor macpro, windows nicely fills one and I can still do mac stuff on the other. There are usb-c adapters that would let you connect your ext monitor and still be able to use the macbook screen.