Benjy probably rolls his eyes at any black ops jokes but then smirks and snickers when Sirius turns his back before playing the straight face again when Sirius turns around. Because they're funny but he's not encouraging them. He'll encourage a lot of other stuff but there's only so many bad puns he can handle before mayhem is called for. (It's possible he has gotten Sirius drunk and left him in an awkward position at least once.)
Abe, on the other hand, rolls his eyes at Sirius (as he does for most of the youngsters in the Order). He probably grumbles at Sirius' antics, which is a tad but hypocritical of him given what he got up to at the same age but it's only because he knows all the pitfalls and would rather other people did not fall into them the way he did. So he grumbles but would undoubtedly stand up for/protect etc Sirius without hesitation. He just might scold him at the same time. :D
Benjy (and Abe) approves of doubts about being a Death Eater and Benjy would definitely encourage those doubts. He's side-eyeing the thing with Fabian though. He does not like seeing friends get hurt. >:( Abe, for his part, understands making shitty decisions and then regretting them later. He's kind of the king of doing that. So he's always there to be an older, wiser voice of experience is Antonin needs it.
Poor Hamish. :( Benjy would probably know of him from Sturgis, I guess, and is unimpressed with the brainwashing thing. Bad Fenrir! Abe accepts any and all into his pub so he'd always serve Hamish a drink and lend an ear.
Benjy sniffs and says that's what happens when you leave this sort of thing to the Aurors. Clearly Hitwizards are superior. :P Abe probably knows his name but unless he's the sort to come into the pub, he might not know anything more about him (other than maybe his DE affiliations if that's known to the Order.)