Love this work. Decided to convert a few sample creatures using your format from Pathfinder to Next (using the DM Basic Rules to compare).
I used Chimera, Centaur, Cockatrice, Dire Wolf, Earth Elemental (Greater), and Flesh Golem.
AC: These didn't seem to correlate well. They tended to be off by about 4 in either direction. Not sure what math would solve this.
Con/Dex/Wis saves: These tended to be off by about 1-3 in either direction. Not sure what math would solve this either.
Save DCs/Attack Rolls: Got it right on.
I'd love to hear of any suggested adjustments for the above so they dont vary so much.