hi renstar,
not really sure about the first two, but I know that when you have a d&c (as I did) which is dilation and curettage- a procedure where the cervix is dilated and then the uterus is scraped to remove the lining, usually done under general anaesthetic, the docs recommend not having sex until the bleeding stops or two weeks, to limit the risk of infection.
Unless you have been specifically told not too, there is no reason not to ttc straight away, we were naughty and started about a week after.
and your last question, no idea but I have heard that too.
hope that helps.
becxxx