@jerza
ha..well, we been giving advice here in the report thread, but if you really want to learn to play better, I encourage you to spend more time in the Strategy & Tips forum here:
https://forums.civfanatics.com/forums/civ4-strategy-tips.155/
This fairly recent thread in S&T is a good example of guy trying to learn to play better...you may want to read it yourself and possibly do something similar:
https://forums.civfanatics.com/threads/asking-for-your-advice-–-shadow-game-on-emperor.643219/
For YT vids, I'd say Lain and AZ are the best as far as learning some new things. Lain tends to be a bit more instructional, but AZ was the guy I learned the most from back in the day:
lain:
https://www.youtube.com/channel/UCBiPHqnZ3mwIqtraltox6jg
AZ...he's actually been playing a bit more IV recently and live streaming it too:
https://www.youtube.com/channel/UCgT_HmP4nlz5wECKOkIlj9Q
As for your questions/points:
1) Currency - While certainly arguments can be made, IMO Currency is the most important tech in the game. (and no..Markets are by no means a reason..I don't build them by the way). The trade routes are obviously one factor - the boost to overall commerce. The option to build wealth instead of something useless indeed has merit. But the most important thing is being able to trade techs for gold and resources for GPT.
2) Whipping...Has nothing to do with bankruptcy and neither does small cities. (population actually increases maintenance costs) Ideally most cities grow to work the cities specials. After initial expansion phase, the cap ideally starts working some cottages and running scientists for the first academy, and being whipped far less. All other cities can be whipped as needed.
3) Monotheism - Not sure what you thought it would help with. Mono is something you can always easily trade for. OR is nice if you are running a religion. I think what this boils down to is having a plan/strategy in terms of teching, as well as understand what the AIs tend to focus on tech wise. I suspect you do not use tech trading well.
4) Great Scientists - Generally you will get up a Library in your cap asap, and run two scientists there for an academy in you cap. Running scientists in other cities as much as you can is simply static beakers, but also leads to future GSs for bulb strategies later. So the sooner you do that not only do you improve your tech rate, but the amount of great people produced sooner, especially with the golden age you run later.
5) Early wonders - Relying on wonders for producing great people is very passive and very sub-optimal. But furthermore, just building wonders without resource bonus or IND trait does not make much sense. And even then, most wonders I use for fail gold anyway if I have any bonuses. Mids are always worth trying for if you have access to stone. GLH has no bonus, but is very powerful on certain maps.
6) Foreign trade routes are extremely important. The basically double your trade routes commerce - more if overseas. You should try to access them one way or another as soon after Writing as you can.
7) Aesthetics can be a good path on IMM+ to facilitate a trade for Alpha and other stuff since AIs tend not to prioritize it as much as Maths or Alpha. I don't always go that route as it may depend on other factors.
8) Primary purpose of EPs is focusing on a known good techer (think Mansa) in order to start seeing what they are teching. This knowledge can impact tech decisions and help facilitate tech trades. Tech stealing is another thing that is probably more dependent on if you happen to pop a Gspy.
Overall, my objective impression of your games leads me to assume that you need to learn some very basic mechanics of the game. I'd assume you likely still struggle quite a bit on Prince/Monarch. Just spending a bit more time in S&T and watching some vids and I guarantee you will start moving up levels quickly. It really boils down to having a completely knew perspective of this game.
edit: Oh..I meant to expand on the 0% and 100% thing. Pom is right in that there is a rounding issue in the game. Check this out in another game early on - after you settle your first city - by raising slider from 0% to 10% and then back to 0%. Notice the difference in GPT vs. BPT when you do this.
So, after you settle your first city is when you start deficit research, i.e., you start losing gold. This is when you start running 0% slider to bank gold to fund the next tech. Banking gold also helps fund expansion as well. You still have the 1bpt from palace, so you are making some, if small, progress toward whatever tech.
After Writing, you will start to build Libraries and run scientists which help even more. After Writing is also when you start hitting the bigger tech decisions...Aesths? Alpha? So running 0% for an extended to allows one to essentially delay the decision, finish Libraries, bank gold, continue expanding. Then use that gold once library(ies) are in to run 100% with the beaker multipliers are in place, choosing the tech that makes the most sense for your game.
A bit later one, the rounding issue basically disappears due to the beaker multipliers and specialists. Again, you can see this later by just checking the slider at 10%, 20%. In other words, there is a break-even point and you will start to see your bpts gained exceed your gpt lost. At that point you have more leeway on playing with the slider a bit, but 0%/100% deal never really loses value. But you will also have the ability to get large chunks of gold later too.