1. Number of unique visitors to DMOZ during last month or an average 30 day period?
I have absolutely no idea.
2. Number of new sites added to DMOZ in 2012?
That's hard to calculate. One can't difference the total listings because several patrolling robots robots remove broken ones from public view. I'm not aware of any script that could sort the wheat from the chaff. Everything is logged so it's certainly possible to write one to analyse and consolidate every editor's activity. That's a non-trivial task and somebody would need to volunteer to write it.
3. Any "clickthrough data", to indicate how DMOZ may still drive some degree of traffic and which sections tend to drive the most traffic?
No idea at all. I can certainly see downsides in releasing the latter info though.
> Also, any word of the plans for DMOZ for the next 1-3 years?
There's a long wish list of bug fixes and editor function enhancements but I'm not aware of any firm or ground shaking development plans. Like any large corporation, AOL plays its cards very close to its chest.