This guy is definitely much better than House Party 4.

Am I correct in saying his "I Got Enough C4" trait will only apply when he hits with Close Combat Expert (barring Perplex or other modifiers)?

Its much more applicable when you run him with the gauntlet.

EE hitting 3+ targets might let him do this too. I'd be interested in searching out an answer. The Joker as Sgt. granting PD and those Police generics that can pack Perplex would make his overall package more appealing. (nope never mind Sgt grants Police TA and Officer targets keyword).

He will become a VERY good piece with the new rules.