What you're referring to is a restricted partner API. And I don't think it's currently available to WhatsApp.
You could request that WhatsApp implement contact tiles, so you can pin contact tiles that open directly in WhatsApp.
(Disclaimer: I work for Microsoft)
I prefer the Facebook app over the people hub for day to day FB interaction. People hub only notifies you of alerts on your wall or from people you mark as close friends. The Facebook app lets you see your full feed. Also, you can't like an individual comment on the People Hub. Finally, it let's you browse your friends profiles and brings more of the ...
I am on WP 7, but this should be only incidental. If it is an option, you could synchronise your contacts to your LIVE account and create an outlook.com-Account (you don't have to use it for e-mail). There you should get an birthday-calendar for your contacts automatically. It should also sync with your contacts, whenever you edit or add a new contact.
The first thing I try for these types of problems is to delink all accounts and relink them 1 at a time, checking to see if the people hub works. Often times issues like this are caused by the oAuth token being revoked by the external service for whatever reason. I won't say that's your problem, but it's pretty likely.
This comes up even if you haven't set up any accounts, and appears to have been introduced with Windows Phone v7.5.
when you first go into the people hub, it will prompt to integrate with Facebook, and choosing "not now" does seem to stop the "f" coming up. If you do choose to synchronise with Facebook, then bets are off, and it will come up.
You might get back all of them if you connect your facebook acount and your Live.com (Windows Live) acount back.
You may go to Settings, and then to |Acounts and then add an acount. Then you have to add the same live ID that you've been using while on WP7. Then you connect via the Acounts tab your Facebook. Restart the phone and your contacts should be on ...
People hub uses your Microsoft account. If on your next phone you use the microsoft account you were using on the windows phone, it will continue to sync (assuming that you will be using people hub on desktop since you will not have a windows phone :P)
As far as I know, you can't do that. Unlike Google Contacts or Outlook.com People, Facebook isn't an address book, you can't add arbitrary contacts or change other people's information there. This isn't a limitation of Windows Phone, it's simply how Facebook works.
I suppose you could get around this by registering fake accounts with the names and contact ...