I was thinking that the best course of action here would be to force the baby to reveal itself. For the baby is a being of two contradictory sides. Lethal danger, and defencelessness. It hides in plain sight, but the second it can be proved that it is an enemy, the fight should be over. The best way I could think of doing this would be for Kakyoin to speak to his comrades secretly, tell them to pretend to sleep but watch from afar as Kakyoin pretends to attack the baby to see what it would do. Honestly, if this wasn’t absurdly hilarious, this would come off far more sad. Kakyoin fighting hard so that his allies don’t die but being treated as if he was insane, unable to save them. I also like to imagine the horror of what this baby leaves behind on its success, a party of men all with their hearts crushed in their sleep... Cool!
The absurd comedy of Joseph feeding Polnareff baby food, love those two together, and then trying to forcibly feed the demonic baby while it holds a whole scorpion in its mouth was a good moment. A great way of tying the tension and drama to the comedy aspect of the scene. That said, with it puking out the scorpion, there is now evidence that Jotaro may have picked up on. Assuming Kakyoin was truly knocked out, I am expecting Jotaro to use the numerous signs of suspicion he has picked up including the potential evidence and try something this next chapter.
I would also like to add some thoughts on the more contrived elements of the story, I have completely accepted them. It feels in tone with the series for the characters to do something dumb, or go off alone to set up the interesting conflict of the arc. It's cheesy through and through and it does it well.