Well, nukes are not cost-effective IMO, since they're not even guaranteed to clear a city of enemy units. You're better off building bombers and carriers to take them on a tour of the enemy cities. I don't think I've ever been involved in a major nuclear conflict.
But whatever floats your boat. )
You mean you didn't know the AI cheats?
The level of cheating depends on the difficulty level. At the lower levels, the cheating favors the player, as AI production speeds are gimped. At the higher levels, the AI cheats really badly. Apparently, that's what "difficulty levels" means for some programmers. <_<
I don't know if the cheating affects the success rate and cost of espionage operations, though.
IIRC, not every part of the spaceship needs the same technologies. It is entirely possible that they were building parts that don't require superconductors. In fact, it's the smart thing to do if you're going for spaceship victory.
Well, that's the point where the game began to get boring for me. The levels at which the AI doesn't cheat (or the cheating favors you) offer little to no challenge once you have grasped the basics of the game, and I really hate it when the AI cheats so blatantly. The higher difficulty levels are there for bragging rights only.