I think you talked to FD agents giving you incorrect information.
1. The new system is not point to point but zone to zone. So CDG-AMS-DTW-CLE or anything of the sort costs 20'000 each way to upgrade, or to fly for free in Y.
2. The above information is correct - upgrade on domestic NW flights for Plat in full Y at time of ticketing, and either through EUA or at the aiport for restricted tix.
3. Confirmations are always different. Just double check everytime and keep calling back until you have confirmations for everything.