What if William has a daughter? Does she move to #3 and bump Harry to #4? Or does the male preference primogeniture part leave Harry at #3 and the daughter somewhere else?
All of William’s legitimate descendants are ahead of Harry.
Example: Queen Victoria succeeded via her father Prince Edward (who died when Victoria was less than a year old), even though he had surviving younger brothers, the oldest of whom (Ernest Augustus I of Hanover) inherited the throne of Hanover, since Victoria could not succeed there (Hanover had Salic law)
Yes.
Probably also the luckiest of candidates as Queen Anne had seventeen children, all of whom died in infancy other than one (William) who lasted till he was about 12 before popping his socks. Any of them could have put the kibosh on George had they lived.
Ah, but if William would have 11 daughters and then 1 son (therefore the son is the youngest in his family of 12), the son would be #4?
For a woman famous for her (possibly platonic) lesbian inclinations, she sure did reproduce a lot. But perhaps the last influenced the first. 
The son would be #3: Charles, William, William’s son. Harry would come after all William’s daughters.