Thanks everybody for answering.
I agree that the best thing to do should be a nut replacement, and I think I'll write to Alembic asking for it.
I could raise the actual nut and work on it in order to adjust it, but I don't like the idea of having an Alembic bass with some sort of imperfection.
About the bridge saddles, I already did what keurosix said.
I even played the Elan for a while, but there was something strange on it.
Now I understand why.
The screw in the middle ain't original since the previous owner took if off in order to revers the nut.
Mica shipped one of that screw twice, I hope to get one at least some day.
I'll keep you updated about the nut issue.
Have a nice day.