In case you're wondering: yes, by Olsen they do indeed mean Jimmy.
You can read the entire crack-creepy story over at Brian Hughes blog, Again With The Comics. I'd have scanned it myself if only I had the issue. Unfortunately, I doubt I ever will, considering that the two copies of Elseworlds 80-Page Giant currently on eBay are going for $375 and $739.99. Yeah, seriously.
As for the story itself, I don't have that much analysis to add. I like that Harvey is depicted as a tragic hero all the way, and while it always sucks to be Harvey Dent, perhaps he's the one who's better off. I've never read Lovecraft, but from what I can tell, sanity must be such a burden.