Did not have the autosaves but part of my regular saves (do not have the save with me being up in happiness) - have fun
Alright, loaded up and took quick a look.
The beauty of a game like Civ5 is how there is always room to improve.
In your game, there are a huge number of things that need work, but most importantly, science!
You are sitting below 200 bpt, and it's t435-451 in your saves.
At a higher difficulty, the game would have been over long ago. In your game it's over anyway as you are a few eras behind France, who's going to win via Spaceship launch soon.
You want to get Libraries up and, Universities up in EVERY city!
You need to build the National College in your main science-producing city (usually capital) ASAP, and it's still not built on t451.
(You need Libraries in all cities to be able to build it.)
You have an extremely wide empire with a ton of very small cities, including your capital.
Many of the cities are not worth having and really contributing little to nothing to your empire, with the roads connecting to them costing you GPT (partially why you are running out of gold).
Frankly, many of them should have been razed to the ground, or puppeted only, with trading posts built around the puppets to help your GPT.
Many tiles have not been improved; you need more workers or to be assigning them to work more important tiles manually.
Trade your luxuries to the AI for gold, or GPT, or for their extra luxuries, to help with your happiness.
You have made only a few trades all game. Especially in empires with a lot of cities, trading luxuries is a huge source of gold and happiness.
As for why you are having trouble with war, it's due to the huge tech disparity.
You are attacking Ethiopia with Artillery and Riflemen (swimming thru the lake no less-never do this when ranged units can hit your guys there) when they have Infantry.
In short, you are way too far behind in science.
Again, on a more normal difficulty, the AI would have likely wiped you out long ago due to how far behind your military is in tech.
I'd also recommend scouting and meeting the other AIs faster; get those ships out to the other continent to see what's going on. Sooner you can meet those other continent civs the faster you can trade them your extra luxs, etc.
Do you have the starting save?
I imagine some people might have time to run thru the beginning and show how a more optimal pathing would look like.