When you plan to use manual port forwarding, you have to enable it in icamsource (not use auto router config). Also, the ports forwarded to each computer cannot overlap. In other words, if you tell your router to forward port 12000 to 2 different places, it doesn't know which one to forward it to. This results in no connection at worst, and inconsistent connection at best. I have a similar setup to you. I assigned my 2 computers a static IP on the local network, then forwarded a range of ports to one computer, and a different range of ports to the other computer (7 udp ports forwarded per camera). Then I enabled manual port forwarding in icamsource on each computer and entered the 2 respective range of ports from above. Manual port forwarding is a real pain to set up properly. However, once it's configured properly, the setup is rock solid...and slightly more secure than using uPNP, which could be a security risk if a hacker were to gain control of your system (not hard for pros). If they can easily open up ports in your network, it's like opening the doors to more attacks/hacks/etc.
As far as the ports being reported as opened or closed...for me, it depended on if I set up a firewall rule or used actual port forwarding in my router settings. I think the response will also vary depending on if there is software listening to that port. If software is not running and listening to that port, it would be like knocking on the door of a house when nobody is home. The door is locked closed, and nobody is there to open it. At least that's my basic understanding of it.
