Usually teenage girls do NOT wear diapers, but in rare case in which they might (bladder problems or infections) then it should be the same way you would change a baby's diaper.
Like any other diaper.
birth father should be charged with abuse.
Respect is earned, not enforced. Maybe you should ask yourself, "What must I do to "earn" the respect of my son?"
The best approach to teaching your teenage son about the effects of alcohol is definitely about the consequences. Drunk driving, impaired memory, these are all side-effects of drinking and your son should be well aware of these before reaching for a drink.
Take the diaper out and wash the clothes again!
No, you should only be curious how to find out if it really IS table salt and not only the cover.
Talk to him about it and make sure he understands how to use a condom.
Yes, she is putting her children in danger.
stop giving him money whenever he asks. you have to be cruel to be kind. He should get the idea.