1) Just for the record, Ulm kicked Ermor's *** in my SP game (Impossible AI, World War scenario, indy 9) with no help whatsoever on my part. Of course, I don't know what theme Ermor was playing, if it was Broken Empire it is less impressive.
2) Impossible AIs on a large map with indy 9 do very well. Indy 9 force them to build large armies rather than rush the start and leave themselves wide open, and large map also give them time to collect the return on their research/site searching investment, and not have to worry about an early rush. The opposite, small map and low indy, mean you can gooble an AI or two and rule the game ever after, especially with a SC Pretender. The AI do know how to cast big spell and search for sites, but I don't know how they might handle extreme settings.
3) I'll late you know how good the AI are at late game when I get there. The problem is, the player is usually quite good at it, so the AI would have to be just as good... The AI doesn't seem to pump more research late than early, but it might be enough.
I am not so far impressed with the AI ability to conquer/jump across seas, except of course Atlantis and R'lyeh. Ermor often conquers a few as well, but that's about it. I suspect the AI knows how to use amphibious troops, but is not good enough at building them on its own.
4) Aye, micromanagement is a bore. Try to steer your game toward things that are automatic (blood hunt, monthly rituals, summoning sites) and having a large cash pile so you can order 5 (or 10) turn worth of armies at a time. Build castles near your borders if you can, and go for massive attacks rather than attrition wars. Anything to reduce micromanagement.
I also like to play with luck 3 and use crossbreedings or other random spells, just for the excitement (oh, look, a basilisk ! and a free castle !).
I treat each turn as a mini-game : play one, take a 10 minute break, then come back and don't try to remember what I was doing, but rather what I should do given the situation I now have
Sure, I forget things, but then I check a castle and find the big army I had ordered, or a summoning site and discover 50 lamias ready to go...