Why Is Abraham Considered a Great Man of Faith When He Had so Much Evidence?

Questions about why Abraham is considered to be a great man of faith when God gave him so much evidence of his existence and a response to the idea that a person’s salvation is questionable because his faith is “all head and little heart.” 

• Since God appeared to Abraham several times, it seems he had more evidence than most to trust God, so why is he considered to be a great man of faith?
• What do you think about people questioning my salvation because my faith seems to them to be “all head and little heart”?