Fukurou is a really interesting character. I think his decision to side with Lalo is a combination of desire to see Kakerou continue to prosper (perhaps even go worldwide with Lalo's connection) and learning into his philosophy of "not closing your eyes out of instinct". On its surface giving control of Kakerou to a hostile foreign influence is definitely a bad thing, but perhaps he believes it is the best way forward for the organization, and is embracing it.
Additionally, perhaps his decision to make an invalid hand here was actually due to going against his instinct as well; he thought something might be off with what Hal was doing, and made an invalid hand on purpose. Because they must choose again if both players make invalid hands, perhaps Fukurou believed that Hal would make an invalid hand as well, and they would get to choose again. His entire being is screaming at him to make the best hand and avoid the Witch Pain, perhaps he went against it to close up some blind spots in his strategy.