Hey, welcome to PPG!
Not sure whether it's the reason, but still: I think Jhasso's dialogue is script-triggered - he should approach you himself. When I do this quest, I always talk to the fatmen-gangers first, then go upstairs, talk to them again, and then they recognize me as a threat, change into doppelgangers and fight. When I go to the basement, all doppelgangers attack me, I kill them, and only then, when combat is over, Jhasso approaches me. Um, I think. But then again, I always have BG1 NPC installed, so this may not be useful at all.
(Aaaand I think that you can move forward in game - you can go and report to Scar without involving Jhasso at all).