This summary is drawn from the Rebbe's letters to him (the late 1940s and about 5720, 1960); I did not find a published biography.
Spreading Chassidus and Torah materials. The Rebbe encouraged spreading Chassidus widely and handling communal funds responsibly (IK 355), distributing Torah materials for communal merit (IK 425), diligence in communication and communal projects (IK 478), and sharing Torah materials with others (IK 7829).
Chassidic memories. He encouraged Reb Shmuel Chaim to record and share personal recollections of chassidic teachings not yet published (IK 7827).
Teachings. Spiritual growth, like physical growth, proceeds in stages and requires introspection (IK 598), and every Jew has true free will because his essence is rooted in G-d Himself (IK 7831).
Sources: the Rebbe's letters cited above.