300 turns at 0% tax rate will increase happiness by 50%. On the flipside, 300 turns at 100% tax rate will decrease happiness by 50%.
Strongholds extend beyond 100%. If you look at a Battle Summary of a battle fought on a tile protected by over 100% defense, you can see that protection can extend up to 180%.
Weapons cap at 99, not 999.
Spy Network also increases the probability of performing a sabotage.
A sabotage negates any stronghold bonuses for one attack. It’s rolled for randomly when spying. The larger your spy network, the more likely you are to perform a sabotage. The larger your target’s spy network, the less likely it is.
Research, launch sites, coins and turns are reset six hours after the first launch. Research is reset to 0, and all launch sites are returned to level 1. If you have 100,000 coins or more, they will be reset to 99,999 coins.
(A common tactic to keep more coins is to buy and upgrade HQs with excess coins. Turns are reset to 300. You can sell them to get some of that money back.)