What should an individual member do when faced with a leading member, teacher, and song leader is living together with a woman of the church. It seems that the entire church is trying to ignore it. I talked to the preacher and he gave a lengthy explanation, saying the member is impotent and that they are in separate bedrooms. This couple also travels overnight together. What about I Corinthians 5:11?
Do I leave if I'm forced to sit before such a teacher every week? Finding another church is near impossible.
You mention talking to the preacher and other members of the church, but the key person that needs to be approached is the two people who are in sin. After all, their eternal lives are in jeopardy. If you haven't already done so, sit down and discuss the problem with them.
While the claim is that they are just living at the same address and not having sex, their actions give the appearance that more is going on. How actions are perceived is an important consideration. "For we have regard for what is honorable, not only in the sight of the Lord, but also in the sight of men" (II Corinthians 8:21). Their actions are communicating that sex outside of marriage is acceptable to them and the church. "But fornication and all uncleanness or covetousness, let it not even be named among you, as is fitting for saints" (Ephesians 5:3).
If the couple sees nothing wrong with their behavior and the church accepts their sin, then you know that you are not in a faithful church. Your choices are to find another church or start teaching the gospel in your community and form a church that wishes to follow the teachings of Christ.