Tanaka never left. He was around during Abyssea, too.
Umm no. He was project lead of FFXIV while a different guy took over FFXI. This was before Abyssea era. New took was responsible for Abyssea and everything from 80~90, including Emp armor. During this time FFXIV crashed hard core, lost tons of money and got some of the worst reviews for a new MMO ever. Suddenly SE announced that the guy doing FFXI would move on as the project lead for FFXIV to rejuvenate it and update it and that the #2 guy on FFXI would step up and lead FFXI, Tanaka's fate was unknown, only that he was "moving on" from project director of FFXIV. Many months of absolute crab VWNM later, Tanaka shows back up and it's been shown that he was doing FFXI all along. Basically they put him as lead on FFXI after the previous guy moved to lead FFXIV but didn't tell anyone.

The timeline is rather easy to follow as is the update style.