My, my, my. Who died and made you God. I thought He was the only one who was supposed to judge, but apparently I was wrong. Somewhere along the line apparently God gave your his powers to judge.
You thought incorrectly. Jesus said, "Judge not according to the appearance, but judge righteous judgement." (John 7:24)
Obviously the fates of all of our souls are in God's hands. However, one cannot be at once a Muslim and a Christian. To be a Muslim is to deny the divinity of Christ. If one converts to Islam, then one has denied the divinity of Christ, even if under duress. Your attempts to personalize the matter don't change the basic facts here.