That's basically just a direct translation of the kanji, since Kuuga isn't really a word. Clear-self or clairvoyant is a pretty good translation that gets the real meaning across imo.
The Lords were around to protect the humans from the Grongi because the majority couldn't themselves and there weren't Agitos back then as they didn't start evolving until recently, which is why the Lords only started attacking in 2001.
Agito was said to take place 2 years after the end of the attacks by the Grongi. That is contradicted by the fact that it is said as early as in episode 2 to be the year 2001, while Kuuga was set in 2000.
Yes, Kuuga ended in 2001, just like most other series until Kiva would end in the beginning of the next year. They also specifically say in Agito that it has been 2 years since the unidentified lifeforms were defeated while the entire way through it is also known to be 2001.