The Law condemns, not saves. It means they are under the Law, not the Blood. If you are under the Blood, you are not under the Law. Like I said(and Jesus),"There is none good, no not one." Your righteousness is as filthy rags to Him. Jesus didn't say there were many ways to God. He said, "I am the Way, the Truth, and the Life, NO ONE comes to the Father except through me."
The part about the heathen family is you are supposed to live a Christian life in front of them and you may get them to repent for their lives. He doesn't want you to get a divorce just because you believe and they don't. You are admonished to not marry them if you are already a believer. There are other verses that tell you if you pray "In the Will of God" He will not give you a "stone", because He is a good Father. What is God's Will?, That no man should perish. If you pray for your heathen family, and you are righteous, He will save your family members. He cannot however contradict Himself, and say I need the Blood of Jesus, but you don't.
Are you willing to convert to Islam, to test your theory?