Celozzi has Oswald in the sniper's nest (firing a missed shot) but I back the fact that he was down in the Domino Room at that moment.
Apart from that, what he says seems very plausible, though I feel that there was possibly some rogue CIA involvement and perhaps knowledge of the hit by LBJ.
That said, what else doesn't hold up in Celozzi's account in that article (wait for the film too!).