I finally took the time to work on the issue that has been killing me from the begining. I could not switch away from my DisplayPort otherwise my monitor would enter in Power Save mode.
See my post:
Yesterday I finally found this post:
And today I decide to get my hand at patching the nvidia-graphics-drivers debian package. See my patch at:
I simply had to dpkg -i install the kernel source, then I followed my own instructions:
I did the module-assistant dance ... it worked out nicely !
I can finally switch to my mac mini on DVI and then back to my debian station on DisplayPort.