Not necessarily.
Definitely yes
tell him he has a small penis
Your husband can show various signs when he is cheating. He might be mentioning his ex in various matters.
If you have absolute proof that your husband is cheating with this other woman then you should deal with your own problems with your husband first and yes, the other woman's husband should know. This is not an uncommon problem and most people (whether a husband cheats with another man's wife or a wife cheats with one of her friend's husbands) is very common and the victim of the cheating generally does tell the husband or wife that their spouse is cheating with their spouse.
You don't; if you love your husband just stop cheating; if you don't love you husband, tell him you don't love him and file for a divorce.
tell him how you feel about him cheating and that you know he's doing it, if that doesnt work buy him a block of chocolate. (I always suck up to my husband to get something out of him.)
Underwear being worn inside outside has no direct correlation with cheating. He might have been getting dressed in the dark that morning. He may have been forgetful. He may prefer it that way. Maybe it was a bet. It's not enough to go on. You need to find more clues that lend themselves to cheating behavior.
No, it is difficult to look at any stains in a woman's underwear (that goes for men) to tell if they have had sexual relations with anyone as women have a discharge just like men do.
Demand the truth, or tell him you're leaving him. No one deserves to be cheated on..
No. A husband with a cheating wife is called a cuckold.
You are in total control of yourself and you don't need permission or even to wonder about talking to your husband about his cheating. Let him know what you know and tell him if he continues to cheat you are filing for a divorce. Take control!
You don't. That's not your responsibility. The infidelity is between the husband and wife.