Yes, it's quite normal. There's a deep sense of intimacy in seeing your partner at their most vulnerable state like sleeping. It shows that you have a strong bond with her.
One possible story could be that while she is sleeping, you notice the peaceful look on her face. It might remind you of all the years you've spent together. You might recall the times when she was there for you during difficult days. Just seeing her sleep soundly can make you feel a deep sense of love and contentment, knowing that she is a part of your life and you are there to take care of her.
Well, it's not uncommon. Your wife might prefer the feeling of no constriction from clothes, which can lead to a more relaxing sleep. However, it also depends on personal habits and the sleeping environment. For example, if the room is always warm, sleeping naked could be a great choice for her.
No, it's completely unethical. A houseguest should respect the boundaries of the host and their family. Flirting with someone's sleeping wife shows a lack of respect for the marriage and the privacy of the household.
One possible reason could be problems in your relationship. Maybe there was a lack of intimacy or she felt neglected. Another reason might be that your friend took advantage of a vulnerable moment for her.
You could try to keep the dog out of the bedroom when your wife is sleeping. If the dog has a habit of getting close to people while they're sleeping, it might be because it's seeking attention or is curious. You can provide the dog with enough exercise and toys during the day so that it's less likely to bother your sleeping wife.
It can be normal in some cases. Dogs often show affection by licking. But it's also important to consider your wife's comfort and any potential health risks. If your wife doesn't like it or is at risk of an allergic reaction, then it's not really acceptable behavior from the dog.
First, you need to ensure your wife's safety and comfort. Then have a serious conversation with the houseguest, expressing your strong dissatisfaction. If they don't show remorse, cut off all relations with them and consider taking further actions if necessary, like reporting to relevant authorities if their behavior is too extreme.