What have been observed effects of inositol in powdered form on schizo-affective disorder? At what dosages?

None. Inositol has proven to be a weak substance for the treatment of any psychiatric disorder let alone schizoaffective which is quite serious.
No real studies. There are no published studies using inositol with schizoaffective disorder. One small study [ http://www. Ncbi. Nlm. Nih. Gov/pubmed/11254020 ] did show that 12 grams/day of inositol could be helpful in bipolar depression. It is more an add-on, rather than solo treatment, for this condition. Another study [ http://www. Ncbi. Nlm. Nih. Gov/pubmed/16449473 ] showed Lamotrigine was more effective.