we do not share your data with anyone and there are many ways to control the visibility and storage life of your data here.
but the internet is a public space and you should always assume your data could be compromised.
be smart with your password, use tor or a vpn, and use pgp for sensitive communications.
No need to worry about strength, it will just last you longer (if you're sensible). Use less than half what you normally would.
Very rare to find anything as tasty, strong and clean as the Pope's!