I took a look at this game. I can't play it because you don't have quick combat on and I don't have a spare 5 hours to watch combat animations.
It looks very winnable to me. Yes, you get attacked by China and the Aztecs (the rest don't matter because they can't reach you), but you should be able to hold them off, even when you become very unhappy. Going very unhappy isn't great but it also isn't the end of the world. -33% in combat isn't that bad when you are fighting a defensive war. Would be nice if you had Oligarchy to counteract the penalty, but you'll do okay. You have tech parity and a lot of units. You might lose a remote city, but that's still not the end of the world. You can't attack your enemy, at least not until you get your happiness under control, but that's okay because you've got good science and good production.
Some suggestions:
- You clearly made friends with somebody. This is a bad idea because sooner or later that friend turns against you and then everyone thinks you're a jerk because your friend doesn't like you. Always refuse declarations of friendship. They only hurt you in the long run.
- You've annexed a lot of cities. I don't think this is a good plan. For one thing, you totally inflate your social policy costs, but you also lose out big time by wasting hammers on courthouses. Keep most of those guys as puppets and you don't have to worry.
- Too many farms! You need more trading posts. Enough said.
- Oligarchy is the strongest social policy there is (taking into account how early you can get it).
- I really like Piety for Darius, but you went Patronage. I'd re-think that next time. Piety would solve all your happiness problems in one swell foop. Also great synergy with your UA.
- I don't know what your plan for that artist is, but he should start a golden age. That's what I did right away when I took over the game. You need the money.
- You are relying way too much on luxuries from your opponents. When they all declare war, you lose all those luxuries and your citizens go into revolt. Don't buy luxuries. Sell yours and buy city-states. Use social policies and happy buildings to keep your happiness under control.
- Many of your cities have garrisons. You don't need a garrison in Civ 5. These units are a waste of money. Delete them or move them to the front.
- Upgrade your cannons to artillery. They are great for defensive wars. Use your melee guys to form a wall. If one of them gets badly wounded, move him back to heal up. Then your artillery pounds on the invaders. This will work great for you.
I'd load the game back up, start a golden age, and get my troops ready on the two fronts. You should be able to handle the game. I guess you're playing for a diplomacy win? Just beeline the UN and you should get it. Good luck!