Anyway, I feel I'm in a strong position now, possibly aiming for either rifles/cats(cannons?) or cavalry/cuirs, and if that doesn't work out I'm pretty sure I could pull of space.
According to the demographics screen, you are last in soldiers, and last in land. Mao already has double the land to work that you do. You're position may be "strong" now, but it promises to get weaker before you cinch the win, if you don't pay attention.
The usual remedy in this situation is to boost your military, and then leverage the military to fix the problem with land.
I'm at a complete loss at what to improve (as evidenced by the tremendous amounts of useless roads). There are a lot of plains and while I know that plains cottage is a bad improvement, I'd rather build it that let my cities work unimproved tiles.
Your workers are running out of things to do because your neighbors are developing your land.
You might be better off with some farms, especially around your production centers. Sure, a plains farm is 2F/1P right now, which isn't too exciting, but it also spreads irrigation, which means you can add some green 3F farms (a little bit better) to take advantage of those mines.
Also city specialization. I'm really bad at this, and especially when it comes to early game. Later on it gets easier when other improvements become viable, but early on I just don't know.
Basic early game specialization: the capital concentrates on research, cities with food and hills concentrate on units, otherwise cities concentrate on commerce.
It's not the only way to do it, of course, but it's a start.
If the map happens to deliver a production monster, you consider wonder spamming there. If it happens to deliver a food monster, you consider turning that into a GP farm. But often these ideas wait until you capture an enemy capital.