Haha crap, I thought I had beaten you. You should have posted your victory.

(but did you also reach 100 percent?

)
Anyways, it sounds quite similar to what I did. I also used tanglevine and fear totems to keep him away to be able to settle and gain some more mana.
But actually the hardest part is conquering the chaos pops together with your starting pops. (without Adrianne getting killed)
After killing the overlord the first time neutrality and law are not that hard to beat, because he doesn't quickly go to other pops and he cannot destroy pops in the castle anymore. It just takes time to really kill the overlord.
But what surprised me was that even when the overlord was totally cut off from pops, he still managed to cast really expensive-mana-draining spells, like champion of chaos, vampires and appocalyps.
I am also wondering what you can do with those mana sprites that you can collect in the middle of the map (only accessible through flying-machine). Because they do not pop up very fast after being collected, so its not like the level with the drums artifact.
Additionally, I can recall that I also got help from the knights against the overlord when I played this game years ago (or am I mistaken). However the knights did not appear this time. It might have something to do with Camelot, using the knights as keys to the pops or bringing them along through the portal.
I didn't use them to open the pops and brought them along the portal, but I guess they must be locked in camelot in order to get their help in the fight with the overlord. Am I right?
But yes, indeed what's left now after completely havinf finished the game... :p