IMO the post flashpoint gear of Deathstroke was meant to make it more reasonable for him to hang with stronger characters. Without it he should not have been able to hurt or survive a shot by many of the heroes out there. With Nth armor prometheum sword and other gizmos i think Bats needs more prep time to have a reasonable chance.
Isis was killed in the fight with the remaining Horsemen, and with her dying breath she teleported Death away and bade Adam to avenge her and Osiris. Black Adam was then endowed with the powers of Isis, adding the power of an additional god to his powerset.
Current Sinestro likely solo's, and together they would subdue Black Adam.
I don't think Parallax Sinestro is who he was thinking of. He should probably clarify, but just because the last time we saw Sinestro he had Parallax doesn't mean we should assume that for current/future battle threads.
Superman and Wonder Woman break through lantern constructs on the reg. Adam is incredibly close, if not on the same level of strength and speed as those two. On top of that, all 4 earth lanterns, combined with hundreds of other super heroes, were unable to contain or subdue Adam in WWIII - no way are Hal and Sinestro going to be able to by themselves, especially given Adam is bloodlusted.
Only problem I see here is the heroes were trying to stop Adam, Sinestro would not hesitate to go for the kill. I get so tired of people bringing up WWIII, besides BA was amped then anyway and MManhunter said there were more powerful fighters on the field but they weren't ready to unleash completely.