Regarding the weather sealing issue, I did a little web searching yesterday to find a few thoughts out there in addition to going to the Zeiss web site. I think the general answer out there is NO, not weather sealed but I found a couple of boards out there where people have mentioned that they've used Zeiss lenses in rain, snow, sleet, fog, etc. with no adverse effects to the lens afterwards. One guy stated that the rubber gasketing in the Zeiss lenses is "special" and prevents climate intrusion. Don't know how true that is.
I had the Samyang 14mm with the Nikon chip for a few months and discovered that I would come home with out-of-focus pics sometimes because when the green focus indicators in the lower left viewfinder switched from > to < and finally land on "o" to indicate focus, the resulting picture would not always be truly focused. It would land on "o" and I could still turn the lens a bit in both directions with it still on "o" which resulted in me not really knowing when I was truly going to get a sharp picture. That's the main reason I sold it.
The tolerences on the Zeiss Makro-Planar T 2/100mm on the other hand are practically razor thin. It's either telling you to turn >, or turn <, or you're spot on focus "o".