Well, it's not really a lot more to learn. It's just a better game in many ways. There's more new civs and wonders and stuff. But mainly there's some improvement to some game mechanics that will make it a better experience. Plus, giving advice on a version no one really plays any more gets a bit harder.
By not being able to see your games, it's is harder for us to really give specific advice. We really don't fully understand where your "game" stands at this point.
So my advice would be to start a new thread over in Strategy & Tips, where really this thread should be, and post your game. Screenshots help too, but if we can open your game it really helps a lot. (screenshots should have resource bubbles)
You can prevent a lot of barbs by "spawnbusting" with warriors. A unit will "spawnbust" a 5X5 tile area. I assume that still works in vanilla. Also, if you are encountering axes you may not be expanding fast enough or playing larger maps..that is another issue.
I don't know what AIs you are dealing with here. I think you mentioned Alex. i would probably have just killed him by now regardless.
I open borders with everyone immediately after writing unless there's an AI that is particular hated by most others. Foreign trade routes are hugely important, plus open borders improves diplo over time. These are things you need to be considering.
I don't know enough about your current situation to make a recommendation of religion. You've adopted one and would not like to change back. Well, then you just need to deal with anyone who objects. I would not worry about wasting hammers on missionaries. Just deal with the heathens.
I don't like chopping forests into axes unless you plan to use them. Otherwise, I want those chops into settlers or workers, or important wonders. Or just save some for later.
Again, really we are giving you advice in a "vacuum". We can give more pointed advice once we see your game.
Keep in mind that we all are eager to see you improve