Your tank was dirty with the 0.2 coils, causing restricted airflow.
You went to 0.25 coils and it was even worse, because the 0.25 coils are dual coil and need even more airflow.
You cleaned your tank, it got slightly better, but nowhere near the 1-2000 puffs you used to get, because the 0.25 coils are dual coils and need more airflow.
Clean the tank up and use 0.2 coils. Sounds like it is cleaned up, so use 0.2 coils. Better airflow because the tank is clean and the coils aren't as demanding.
If you want to use 0.25 then get the bubble glass.
Best of all, get the bubble glass and use the 0.2 coils, I found that combo works really well
I know how frustrating it is when this happens. It's happened to me a few times, things are just perfect then something goes wrong and you can't figure out what it is, and all you want is for it to go back to what you were enjoying. Hopefully a clean tank and not so demanding coils will get you there.
Good luck!