Sorry, i meant to get to this one earlier.
There's more than one option in windows display settings to disable monitors. Windows should be able to turn off the use of them, or, hopefully, turn off detection. It's not always straightforward to do the latter, but it's normally possible. If this fails for whatever reason, hit the identify button to see your actual physical monitor's display number "x", then set MAME to target \.\DISPLAYx - this should help switchres find the right display. If not, open ArcadeOSD and hit the 2 key until the program is on the monitor you want, then hit the 1 key, and it will show the name/number of that display. Which, as you've noted, climbs when you reset the video card, so you have to restart and get the lowest number.
The next step might be to see if you need to clone the displays to help other emulators if they can't be targeted. Most other programs won't have any trouble with a cloned display, but the switchres utility that GroovyMAME uses might not be so happy.
Please report back with results, it sounds like an unusual bug