This summary is drawn from the Rebbe's letters to him (about 5717–5730, 1957–1970); I did not find a published biography.
Supporting Chabad work. The Rebbe encouraged him to use his strengths and influence for spreading Judaism and supporting Chabad activities, including Kfar Chabad (IK 8704), thanked him for his ongoing help to the community and urged him to increase it (IK 9652), and wrote about Yud-Tes Kislev as the new year of Chassidus, a source of renewed chassidic warmth (IK 6019).
Unity in communal events. The Rebbe expressed a firm negative position on organizing a global synagogue convention (IK 9427), and taught that unity must come first when organizing religious gatherings, avoiding anything that would cause division (IK 9450).
Simchas Torah in Jerusalem. Several letters are the Rebbe's messages to the Simchas Torah celebrations in Jerusalem, on the unity of all Jews in the joy of the Torah (IK 9579, 9760, 9997).
Sources: the Rebbe's letters cited above.