Canadian monarchist here - my mother idolized Queen Elizabeth!
1. The Queen has said she'll never retire so that remark about age 95 and abdicating in favour of Charles...
2. Charles will be king. He actually seems to be more settled since his marriage to Camilla.
3. In the 30's yes King Edward had to give up his throne to marry an American divorcee. However the "rules" have changed. Charles will be king even with his divorce and remarriage to a divorcee. The Queen has really advanced the position and customs that the family follows.

In thinking about the Royals it seems to me that it was unfortunate that Charles was not allowed to marry Camilla when they were young. For one thing, lovely Diana would probably still be alive. For all the luxuries they sure have some weird rules.
And yes, the rules have relaxed a lot in the past few decades. I read that when Princess Margaret got divorced it paved the way for more relaxed attitudes about it. Out of the Queen's four children only one has not been divorced.