Common dosage for 4-AcO-DMT is 15-25 mg according to
PsychonautWiki.
Harmala dosage depends on several factor, you will need to experiment. It's better to use extracted harmalas for more precise dosage (also described on many places).
You can expect something 2-4 fold increase in subjective effects from the substance if MAO is strongly inhibited, so use lowest possible dosage of the 4-HO-DMT.
The active compound from 4-AcO-DMT is psilocin and mushrooms+harmala combination is described - research pharmahuasca and then adjust mushroom doses to pure psilocybin/psilocin doses.