While its difficult to follow exactly what you are doing, you may want to make your connections with IP instead of hostname when multiple NICs are involved, example:

Sean Drohan
Stardock Support Manager

I just made the change suggested and am using the IP address associated with the Ethernet.  Unfortunately it didn't work.  What happens is the functionality of the mouse stops working immediately when the 2nd screen appears.  The only way I am able to disconnect the WiFi displays session is by using the touch screen.

I'm not sure what info I can provide to make it more clear, as you stated "its difficult to follow exactly what you are doing".  I tried to be very clear and detailed in my original description of the problem.   Please let me know what else you may need to be able to recreate this issue on your end.

Sean, I reviewed the link you provided and then I performed the following steps, which unfortunately did not resolve the issue.

1. I made sure the firewall on domain, public and private profiles was off, on my main pc and secondary laptop
2. From main pc I made a connection to my laptop using the Connect feature.  WiFi is turned on both machines.  In addition, I have the IP address associated with the Ethernet specified in Multiplicity
3. Once the connection is made, the desktop from my main pc is extended and visible on the laptop.  This is the point where the mouse cursor disappears on both screens and no matter how fast, slow and in every direction, the cursor never becomes visible.
   
   
4. Since the laptop is touch screen I can exit the session and all mouse functionality returns as soon as the secondary screen is no longer being projected onto it.