However, the actual data retrieved from your Facebook profile (wallposts, friend lists, etc) is deleted after 1 hour -- unless you enable Historical Analytics, obviously.
There is no contradiction here.
2. This question is phrased in such an insulting way I can't imagine you aren't deliberately trolling.
3&4. We've been quite upfront about what we do with your data. All your Facebook data goes away unless you opt in to Historical Analytics. Otherwise there is no PII derived from your Facebook data that we keep. You can disable Historical Analytics at any time, and you can disassociate your Facebook account from your Wolfram ID at any time, too.
To sum up: we've taken the high road from the beginning. Unlike many FB-based businesses, users aren't the product here, they're the customers.
At $600/hour for a lawyer and 30 minutes of their time to add a sentence or two, it'll cost $300 to make the changes. That's well under however much your time cost to make unbacked assurances online. And at the end of the day, your service and your users will be better off for it.