Walaikum Salaam warahamatullah wabarakatuh, In shaa Allah check out sunnahonline, it has the biography of sheikh Uthaymeen, 12 years ago Dr.Salih As Salih interviewed Sheikh Uthaymeen's wife and she gave the biography of Sheikh Uthaymeen on paltalk. It should be in their libaries or achrives and salafi bookstore has the book ''The Life of Imam Muhammad Salih Bin Uthaymeen The Salaf. In shaa Allah, this will help. May Allah grant you success. Ameen