(1) Yes. Relocking/unlocking wipes the SDcard. If you unlock for this, my suggestion is to keep it unlocked. That way your SDcard remains intact. If the update comes out and you want to take it (which should really only be a preference if it's different than this one, IMO), you will probably need to be on IMM76Q. We will know when it comes, but like I said earlier--if it follows the what's happened here with this and what's happened before with the IMM76K leak, then that will be the case.
(2) In theory, if you're already unlocked and on IMM76K--yes. If you aren't, then no.
(3) If you prefer the stock recovery, then you need only to "boot" the CWM recovery instead of flashing it. You will need that recovery in either "flashed" or "boot" form in order to flash these packages. In the video I explain this a bit--how to do it, what that means, etc. Also, due to a file associated with the stock recovery, the stock recovery automatically "reflashes" itself upon boot unless this specific file is removed. That is an option in CWM6, as demonstrated in the video (choosing no = reverts to stock; choosing yes = keeps CWM).
For the third question, if you choose to boot, simply change the fastboot prompt from:
Code:
fastboot flash recovery [nameofrecovery].img
To...
Code:
fastboot boot recovery [nameofrecovery].img