And now I am not convinced they will will drop it just because IMF said that they won't support that.
IMF indeed lends money to the smaller/poorer countries, but they quite often ask for various things to be done by the governments, things that are usually far from nice/popular, hence it can easily lead to IMF getting turned down by governments. It has happened in the past, it will happen in the future too.
All in all, it make no sense at all overthinking and panicking because of this.
The president (Nayib Bukele) is very adamant about Bitcoin, and he is not going to drop his plan just because the World Bank or the IMF doesn't support the idea. Even if they somehow bully El Salvador to roll back the changes, how long this status quo is going to last? A lot of governments are unhappy with the sharp rise in the US Dollar monetary supply in the recent times, and the reduction in purchasing power that was associated with this. El Salvador is a small country and may be forced to fall in line. But what they will do, in case Saudi Arabia or Japan does the same?