PG-13. Probably a hard PG-13, tho. And I'd call an R-rated cut basically guaranteed at some point.
But one thing, I really don't think it tells us anything about the extent of his involvement? We know there's a scene where he tortures Harleen, another where he and Harley take a dip in the acid, another with him and Harley in the Jokermobile, one more where he's torturing a Belle Reve guard, which is weird, and then there's everything with him in the tuxedo, and I've got no idea what's up with that. So there's still a fair few questions.
Looks more like soldiers covered in black gunk. You can see they're carrying AR-15s, and decked out in what looks like military issue helmets and gear. I'm thinking they're the first group that got sent in to try and figure out whatever the hell was going on, then the Squad got called in when they were... turned, or something.