Christians, when you obey the Lord, does he give you unmistakable peace....?

Yes, and if I don't, then there is no peace in my spirit. Peace is the umpire for whether we should or should not make a decision, or act. God said all whose minds are stayed on His shall be kept in perfect peace in Isaiah 26:3. This is because we trust God and believe His promises. Romans 10:8-10 is how to be born again.