I happen to know people who are followers of Christ in other religions.
God is far more interested in what you are than who you are.
Whenever you serve others in any way, you are actually serving God.
The closer you live to God, the smaller everything else appears.
Read the genealogy of Jesus, and you have to see how the four women in that genealogy God used their sins for His glory.
What is your assurance of salvation? The promise of God's Word. If God says it, that settles it, because God cannot lie. You can trust the promise of God's Word.