I loaded up your first game because I wanted to see what a Cottage Economy looked like, and I noticed a few things that I would consider "mistakes":
- Both opponents have money sitting doing nothing, and you have spare resources to give them for it. That's 13 extra gold in your pocket!
Perhaps... I can't remember what was going on at the time, but I ended up getting what I needed from Shaka later.
- They both have resources you could get. Unless you're planning on attacking FDR right away, which you shouldn't, since your forces aren't close enough.
I ended up attacking Roosevelt very soon after that save, and I didn't have any problem. It's hard to know just how much military they have, but the "powergraph" is not a good indicator. Things like having the Great Wall will boost that a lot, but how does that make you stronger? Either way I kicked his ass... take a look at my last save. 
- Shaka is willing to sign Open Borders. Why didn't you do it? More Trade for you.
I guess
- You've got uncollected Silk that could be traded (you're short 1 thing to trade). Oh wait, I see, that's a new city.
I have enough other resources for trade, so I decided to keep the forests for preserves later on. This may have been a mistake though, since I have enough free specialists in that city for my National Park to get me engineers, and I can't get more than 5. (1 with forge, 2 from factory, 2 from national park + free one from NP)
- You need a few more Workers and to throw out a couple Settlers to grab some more resource nexuses. Overall, you placed your cities well to grab them.
Damn right. I think that was my biggest error in this game, I was really short of them.
- I was going to say something about Grocers, but I see you're taking care of that. (I also see a Settler being built now. Good.)

- You don't need Walls. Ever. (Pretty much.) You're not Protective, you haven't got Castles anywhere, you're not Spanish. But since you've got ToA in your capital, you could stand a Castle there (or could've - might be too late now).
I'm starting to realize that. I usually never build them, but then I realized that they boost your power, so maybe it would prevent me from getting attacked a little. It was probably just a waste of time.
- You have a lot of units sitting around idle in your cities. Except for holding back a couple or so, you can put them all on the front, maybe build some boats and raid the enemy rear. AIs are rarely smart enough to do that, and incursions can usually be dealt with by that small reserve and any new units before they head to the front.
I think I was using them for HR, keeping the people happy at the time.
- FORGES!!!! For the love of all that's lovable!!! You'll boost your production another 25% AND provide an extra Happiness with your Gems.
I used to never build them, being afraid of the -1 health, but I can see that was a mistake!
- You know you can have more than one thing in your build queues, right? Unless you're using that to remind yourself to monkey with your tiles now and then, save yourself some hassle and queue.
- Serfdom? Build more Workers, then you can go to Slavery and start whipping! Oh, wait, you haven't Farmed much; stick with Serfdom.
- No Vassals? Shaka would probably be your attack dog now. FDR would probably fold with a solid hit too, letting you save your meager production.
I haven't been able to play successfully with vassals yet... maybe now that I'm more familiar with all the BTS stuff I'll give it another shot. It may save a lot of time.
- Lots of unupgraded units.
- You're breaking even at 30% gold WITH a Golden Age going.
Is that bad?
You're already in a GA, no need to spend your guys on extending it, but since you've got MoM, kick it off when you've got most of the continent under control.
Also, I don't know how much of your lack of productivity is due to playing at Monarch compared to my typically Noble games (started playing Prince a few games ago), so maybe your lower capability compared to what I expected can be blamed on that.
Feel free to smack me around as you explain why I am completely off base.