I know you didn't address your question to me, but I can't resist replying.
Our Father in Heaven would be disappointed of course, but he also will defend us against our enemy in the end. (he is our guide as parents...all Christians sin to the end) The only sin that is unforgivable is the one of non-acceptance..or failure to accept Jesus, and become a child of God.
I have to think the man's status with God is more important than what he professes. Fear is an enemy...and not all believers' faith is strong. Maybe he was still a babe in Christ..and hadn't learned enough about martyrdom yet?
Luckily this man still has more time to get it right with God.
I don't think I could do what this man did --- especially grabbing the Koran and passing it off as something I could believe in --- I might grab it and try to quickly find the parts where the "people of the Book" are discussed and try to use one of the Muslims' own lies to save my life --- that THEY are supposed to accept the people of the Book so that they shouldn't behead me.