There's no way it could automatically renew unless a recurring profile was created at PayPal and PayPal paid it, which CBSubs would respect the payment and renew them. If the plan never had recurring payments and no recurring profiles exist at your payment gateway then there's no way for it to renew automatically.

There is a grace period of 7 days upon expiration of membership.

The subscription will not truly expire until your grace period has ended so it'll still be marked active.

Subscribing 01/01/2017 and expiring on 12/31/2017 is correct as that's a full calendar year and you've it set to by calendar year. The 01/01/2016 expiring 12/31/2017 appear to have been renewed at some point, but the last renewal date isn't set so I've no idea what's up with those. Was the payment gateway or plan parameters changed at any time while users had already subscribed? Changing gateway parameters and plan parameters while a user is already subscribed doesn't have an affect on existing subscriptions in most cases.

On the CBSubs > Subscriptions page click the # under the Id column to edit the subscription. You can manually change the dates of the subscription there. I still don't have an explanation for those renewals unless the users did it themselves.