I am still in my game, surprisingly. I made one more session.
I would take more advice, for future games. As I was attacking Sidon, with my entire army, Suleiman settled a city next to the army. Next turn he complained I was too close to his borders, and was I going to attack him? It was a horrible place in the game to attack him, so I said no. A few turns later, I did need to attack the city and now have quite a relations hit with all other civs.. What's best to do in this case? As I did, or to declare war immediately? If there was only 1 or 2 civs left, its a different picture, but my first war gave me a negative relations hit.
The answer depends on many things like number of troops in the vicinity and quality and health of your units. Purely from a diplomatic standpoint, it is of course better to declare war right away but your troops need to be able to handle the fact that the AI get to attack first. The right moment to attack might have been on the turn before Suleiman founded his city.
Attacking England is another thing. Usually they are easy to deal with before t100 (or rather before Longbows) or after t200 (when you probably have Battleships to kill the SotLs). Advancing with Crossbows against Longbows is in general a pain (until you get range on your units).