Beautiful collection! I really love the IWC and Longines in your collection - would love to see pics if possible.
As for the Pam 000, 005 or 112... I would personally go for the 112. I love the clean dial of the 112 without the small seconds sometimes.. its so classic. The sandwich dial of the 112 over the 000 is selling point for me, especially as a first PAM. As for harder to get, I suppose it depends.. the 112 has more production especially since it has been around a bit longer, and more are made every year... but if you want the secondary markets, the 000 seems to come up for sale just as often and is a bit cheaper. I would say the 112 is more popular, however, I don't think you could go wrong with either.
Hope that helps