Oooh very good questions here.
I haven't used MH in a long time. I've switched to OpenHAB myself.
Of course, I don't work for Lockitron/Apigy.
That being said, to lead on the right path-
1) re-API, yes, you'll want to start coding for API v2 already. Make sure you sign up for the developer mailing list, and that should get you access.
2) The API v2 page will help you get the access token, your "application" registered, and show you your actual locks.
3) To my knowledge, right now there is nothing in the API documentation regarding state. It just shows "null", but it is part of what's returned when you list all locks, or query for a particular lock. This could be happening in the future. That's more for @cameron or @pmg to answer.
There is a way to use webhooks to have your system notified when an action occurs. You can also poll for the last 10 activities (locked with app, unlocked by hand, etc).
You can also always issue an action (i.e.. Bed time scene issues lock command to Lockitron), and if the lock is already in this state, it will just return a standard error. More is in the API v2 docs.