Lastly, I would explore explaining away the ineffectiveness of the gas in Jabba’s subsequent subtitles, something to the effect of “you must think us fools to try that old trick”.
I was thinking something more to the effect of “You fool. [Gas name] gas has no effect on hutts.” Then again, everyone around him was fine too, so I guess that wouldn’t work. That said, your line wouldn’t be any better, since it doesn’t actually explain why they weren’t affected.
I didn’t have the whole scene in front of me so I didn’t want to write too much, just give a sense of direction. The idea was that they were prepared for the ploy… I’m sure with some effort we could collectively come up with an explanation. 😃