In the end, Jack doesn’t seem that damaged, he swallowed all that impact from Zunisha’s trunk.. what a beast!
He also look even more of a beast without his mask. So Jack is a Fishman? Too bad he can’t swim anymore because of DF , anyway he is able to breathe underwater.
Also now that everyone left, it’s a perfect opportunity for him to go back on Zou. It seems that Law and Zoro already left to boot, only leaving Inuarashi as capable one and even him doesn’t seem to be in that great of a state. What if he ends up capturing Momonosuke?