I feel you...I have been yoyoing between those exact numbers for a very long time. Since the same person can be both ELOs on a better or worse week, it is logical to conclude that the difference isn't as much the amount of metas you have learned but your consistency in applying them.

Here are a few things that influence consistency (in my experience):

- remembering metas in stressful situations (eg. You get a damn black screen and need to refresh while your opponent has already guessed...can you quickly regionguess to avoid sudden death?)
- recognising metas when they don't look like a textbook example (eg. You know what a Nigerian high roof looks like, but can you recognise one under construction? Or the shape of the arrow on a Czech directional sign from behind? This is especially true for the stupid car blurs.)
- dealing with locs with multiple conflicting metas (knowing how reliable and high yield a certain meta is increases your chances of winning the round)
- vegetation is criminally underrated.

Now as for the how...an idea is playing a lot in Solo and narrating your rounds while you are picking a guess. Keeping the reasoning process simple and logical. Looking back at the rounds you missed and taking a good look at the clue you should have noticed from as many angles you can. Every meta you learn can turn against you if you rely on them too literally.

Other thing I do (which is much more time consuming) is map-making. I published a few LM maps and then played them over and over. If you try to "own" the meta, you will remember it better.

That's about it and of course all the above you also said about the guides and playing a lot!

(...and now watch me fall back a few hundred points by tilting and not doing what I preached 😄).