How can I mix Bitcoins with minimal fees? So that the output is pure AML.
I don't see correlation between minimal fees and pure AML (as in "clean" coin). You might find mixer which claim you receive "claim" coin, but it can't be verified especially because each service may have different way to determine whether certain coin is "clean" or not.
Is it possible to split the transaction into many small ones?
It's possible by creating multiple mixing request, but that means you pay more for TX fee and fee imposed by mixing service.