Re: Q1, until *real* answers appear.

You probably know this already, but on the off chance you don't, there are a lot of interesting tidbits in [here][1]. (Group Representations, Ergodic Theory, and Mathematical Physics: A Tribute to George W. Mackey) One of the papers in here (the one by Kirillov) contains a simplified proof of the imprimitivity theorem in the Lie group case. 

There is also a survey (the article by Judith Packer) of projective representations and the Mackey obstruction. 

There is also an article by V.S. Varadarajan (posted on his website) about the work of Mackey, but the UCLA website seems to be misbehaving right now, so you'll have to check this later.


  [1]: http://www.ams.org/bookstore-getitem/item=CONM-449