Following a comment by playerfanatic, I went and checked the difficulty levels requestor in the Conquests editor and it turns out that on Sid level, as well as a large number of starting combat units and a research capacity 2 1/2 times faster than yours, each AI civ starts the game with FIVE settlers! No wonder Sid is so hard. BTW the next level down, Deity, the AI civs start with 3 settlers apiece. Personally, I think I might step down from Monarch to Regent level. Regent puts you on par with the AI civs, and I think I'd like to play at this level for a while to get a true picture of how well I'm doing in comparison to the AI.