Quick recap of what I did so far:
1. Settled in place. Founded a couple nice cities for the strategic resources and rushed Charlie. Wiped him out in the BCs and then the economy COMPLETELY crashed.
1A. Researched Code of Laws on my own, while the rest of the world each researched two or three other things. I then turned around and traded CoL for 70% of what I needed to get back in the race. I then used a Great Scientist to bulb Philosophy and used that to trade my way all the way back up to second most advanced. :

HEW:: That worked out well.
2. Founded just enough cities to seal off the entire swath of land from the gems and iron southwest of Paris all the way to the Roman border.
3. Spread Charlie's religion as far as I could and built the shrine. Also, I cottaged the hell out of my empire, especially all the river cities.
4. Opted to adopt Izzy's Hindu religion rather than my own, which kept Izzy, Vicky and Bizzy from attacking me while I built improvements while they built units and waged constant war with the Vikings and the Celts.
5. Tech path headed for the cottage friendly things, with the thought that I would be able to surge WAY ahead and maybe even pull off the old Tanks vs. Longbows move late in the game.
So to pick it up from where I left off, once I got Democracy, things really started to look a lot less scary. My friendly status with Izzy, Vicky and Bizzy (pleased with Rome, Bizzy's vassal) has really come in handy. I started building tons of cannons, muskets and Macemen and quickly vassalized the Vikings before anybody else could do it. I then turned that stack around and headed for England.
She was friendly, but also a complete pushover. Meanwhile, the Germans and Celts were having their own massive war, with both of them having a higher power rating than me. This is a very good thing.
So, I vassalized Vicky after taking one city and then giving it back. She went right back to pleased with me. The next thought was to do the same to Izzy, since Bizzy's power rating was still right around mine. Then, after researching Physics and Steam Power, I went back and researched rifling while my stack moved back to get ready for Spain. As I upgraded 30 or so maces and muskets to rifles, I changed my mind and decided to deal with Bizzy first.
Two reasons for this: His power rating just took a nosedive, no doubt a combination of my rifles and massive losses to the Celts, and HE was researching rifling. Right after his power rating nosedive, Rome broke free from him. Sadly, all of my troops are on the other side of the world, or I'd make quick work of JC. I could make good use of those cities. I'm sending some fresh cannons and rifles over there now. I will not take him as a vassal, so I need enough troops to finish the job. Hopefully I'll get a bunch of level 4 rifles out of the deal to get some amphibious troops and take out Atlantis soon.
After I make the German border cities my own, I'll probably take him as a vassal and then do the same to Izzy.
That makes it the world versus the Celts.
While the German and Spanish wars are going on, I'm going to research railroad (half done already) and then artillery.
I SHOULD be able to pummel the Celts with a giant stack of rifles and artillery, but it is possible that he could mount enough of a counter attack to seriously damage all of my city raiders. I'll make sure to scout ahead before I do anything stupid. If it looks a little shaky, I'll wait until infantry.
Overall, it's been a tough little game. I had to incorporate diplomacy. I had to set strategic research paths to first save the economy and then drive the economy. And I had to be very patient with my strategy.