I believe CivAssist will run on virtual pc on the mac, albeit somewhat slowly....
Top shield producer is currently Halls of Mandos with the Iron Works, then Husborne Crawley. I haven't worked our what the maximum output is though, too late tonight, I was just about to shut down. I would guess though as Halls of Mandos has little in the way of extra food, while Husborne Crawley has it coming out of it's ears that Husborne Crawley would be able to support a much higher population and hence use more of the high production tiles around it giving a higher ultimate output. It needs more than a guess though.