Aye, Its been quite awhile since I've played too so I can't say for 100% certain but I believe there's dialogue regrading it. As for other councilers, who knows. We don't really know whospart of the council, or how big it is. Could be that during the attack they were caught up in sieged cities or even outright killed.
Well I think that the number of councilman are the same number of chairs in the room. As for the Imperial councilmen, it's plausible, but I figured that the entire council would sped almost all the time in the Imperial city, and if there were any that left, besides of the Non Imperials, to another city, that would be a very few. That's why I suppose that they are hiding somewhere from Mythic Dawn Agents.