Is it permissible for the wife to insist on knowing her husband's phone passwords and to boycott him until he agrees, and what is the ruling concerning a wife who accuses her husband of committing an evil deed without proof and quarrels with him based on this?

A wife has no right to insist on knowing her husband's phone passwords. If she boycotts him for this reason, she is unjust and harms the marital relationship, and the husband has the right to discipline her. Neither spouse is permitted to accuse the other with ill-suspicion without evidence. Both must treat each other with kindness and good assumptions.