Clearing your cache will not destroy your cities it just removes Old stored start up data so the New data can replace it.
Why do you have Storms On in BUG? They slow down your game. Not really recommended by the team anymore.
So Noriad is a regular watcher eh.
Disease if kept below 100 will not be noticeable. But as it climbs and more disease are activated then it can get dicey. By level 400 you will need to give it serious attention. Cholera is activated at the level and can be the 9th disease stacked. Prehistoric Era does not allow all disease to be active. By Tribalism 5 will be activated. You can get 9 of them going when you research Animal Husbandry.
When you get to Sedentary Life 6 more will be activated. Last disease activated will be at Polytheism. Total 16 diseases.
So for right now in your game, levels below 175 will not impact you much at all in



, just in more

and

. Once you reach Tribalism and then Animal Husbandry higher levels of Disease will start to mount up the penalties. The



reductions do stack/add up.