Sure. In a story, the wife's friend convinces her to go on a trip with her during a time when the wife was supposed to be helping her husband with a big project at home. The wife gives in to her friend's persuasion and goes on the trip, which causes some friction between her and her husband.
Definitely not. In modern society, we uphold the values of individual autonomy and respect in relationships. A drunk person is not in a state to make proper decisions about such intimate matters. So, for a husband to share his drunk wife with a friend is not only unethical but also a form of abuse of the wife's lack of capacity at that moment.
This kind of description is inappropriate in the public domain. We should focus on positive, healthy and respectful relationships in stories, not such improper content.
He should focus on her pleasure. Listen to her body language and verbal cues. If she seems to respond well to a certain touch or action, keep doing it. For example, if she moans when he kisses her neck in a particular way, he should do more of that.
This is completely unethical. A marriage is based on loyalty and fidelity. Such behavior violates the trust within the marriage relationship and goes against basic moral principles.
This is completely unethical. A friend's wife is in a committed relationship with your friend, and any form of sexual interaction outside of their marriage is a betrayal of trust. It can also cause great harm to your friendship and their family.
This is completely inappropriate. A wife's sexual relationship is a private and exclusive matter between her and her spouse. Involving a best friend in such an intimate aspect violates the boundaries of marriage and proper relationships.
One story could be that the wife and the husband's best friend both share a love for painting. One day, when the husband was away on a business trip, the best friend came over to drop off something. The wife invited him in and they started talking about art. They ended up collaborating on a small painting for the husband as a surprise. It was a completely innocent and positive interaction that strengthened the bond between all of them.