Why are the people I’ve circled not showing up

You can't stop people from adding you. If you don't post public you have nothing to worry about, they will never see a thing. If you post public even people who have not added you to their circle will see the post if they visit your profile. Even people who have not joined Google+ will see it. Public really means anyone. So either way you have nothing to worry about people adding you to their circles. It makes no difference at all.

If you have added people to your circles using email addresses, and those people do not use Google+, they will not show up as "in your circles" on your profile. This explains the different numbers you see.

I cannot find a way to hide the fact that you are in someone else's circle.