The major issue I see with this save is your lack of city specialization. Most of your cities are cottaged and I don't see any clear-cut production or GP farms. Paris has a nice amount of food and instead of working all those unimproved tiles, you could be running specialists for a much better yield and many more great people. Also, you're in representation which makes running those specialists all the more effective. In commerce cities like Antium, don't farm the river tiles. Cottage them as all riverside tiles get an extra commerce. Those cottages need to get up earlier too, by 1500AD most of your cottages should be matured into at least villages.
You're working unimproved tiles in plenty of cities, which either means you don't have enough workers (13 for 13 cities isn't terrible, but most people use the 1.5 workers per city rule to keep on track), or you're not using them effectively. Improve cities as their populations increase so you're never working unimproved tiles. The extra growth can either go towards running specialists or you can whip them away for massive production. Also your tech path is a little strange, but I'd have to see the early game to assess that. A good indicator at your level is to try and get liberalism by at least 1000 AD (maybe a little later if you're slingshotting to steel or something). I don't generally research theology (unless I'm going for an AP cheese victory) as it's a priority tech for the AI and easy to trade for. Also check your civics, Serfdom might be good as of right now as you have plenty of tiles that need improving, but you're not running a religious civic - organized religion or pacifism could really help you out right now. Also, don't forget that when running representation you want to run as many specialists as possible, so caste system might be a good idea too.
Regardless, you've got this game in the bag. You're already halfway to a domination victory, I would just take out Alexander and/or settle some of those islands to finish the job.
Oh and try to concentrate wonders in certain cities. They give you GP points, so building a number of wonders in the same city will make GP spawning occur much faster. Try to avoid crappy wonders like Angkor Wat unless you have a really good reason.
I'm editting on the fly here, I keep finding other things to point out: Civil Service should have been teched a long time ago. Not only does it give you the ability to chain irrigate farms, but it gives you the bureaucracy civic which is extremely powerful in the mid game.
