This summary is drawn from the Rebbe's letters to him (about 5720–5726, 1960–1966); I did not find a published biography.
Books for soldiers and the public. Much of the correspondence concerns publishing Jewish texts. The Rebbe encouraged producing a high-quality Tanach for IDF soldiers that they would use every day (IK 7170), noted that even small practical enhancements — such as a ribbon marker in a sefer — increase people's engagement with holy books (IK 8596), and thanked him for books he sent and for help with a library (IK 8751, 8928). He wrote that Jewish memory must lead to positive action, and that publications should spread eternal Jewish values (IK 7446).
Torah above politics. The Rebbe stressed that holy objects such as Sifrei Torah must remain above political interests and never be used for partisan ends (IK 8971), and that prayer customs should stay true to tradition rather than be unified artificially (IK 9049).
Torah and science; leadership. He wrote that both Torah study and scientific inquiry aim to uncover hidden powers within creation (IK 8831), and that true leadership roles require inner motivation and cannot simply be assigned, as when a community must fill the place of a leader who has passed away (IK 8699).
Sources: the Rebbe's letters cited above.