If the KVM connection is only opening on your main monitor, could you try using the KVM connection in windowed mode, then dragging it to the monitor you'd like to use it from? Once you disconnect, then reconnect, does it open again on the desired monitor?
When I go windowed and dag it to my second monitor, I can fullscreen it again, and it shows its on monitor 2, but when I close it depending on how I open it, it will either open on my 1st, or open but not visible still. Am yet to try Multiplicity 4, as I have the steam version of 3, and don't intend on buying a new copy for $92 just to fix 1 issue, if that be the case I'd just go back to using seamless mode.
How many displays do you have showing in display properties?
Only the 2 displays, which is all windows is showing. no software to control the displays or anything like that.
It's just strange how Multiplicity KVM is the only thing that is having this issue. Have also sent you link to dxdiag