Huh, I wonder why Finn suddenly had a change of heart. Trying to show that he's still not a spy? Only Rey and BB-8 know about that for sure and, coincidentally, they're nowhere to be found. Yanni was super suspicious of Finn before they even left the Falcon however, so it probably won't work that well. Or possibly Finn thinks the Resistance could use him to feed the First Order information and keep him alive longer than if he simply goes back to the First Order. Probably that one; heck, if the info is actually useful enough, Kylo Ren might not even try to kill Finn when he reports in next too.

As for Chewbacca's point, there's a very easy way to solve that. Grab Kanata and hustle him to the Falcon on the premise that this bar is going to be all shot up soon. And that they're going to get death sticks and drinks at a better bar somewhere else, one that might even serve the famous (and now quite rare) fish-grease alcohol. Oh and while the ship is flying to the next bar, politely ask for a better explanation of the map, that wouldn't be too hard right? The upside of this plan is that it might even fool Jim into going along with it without accidentally wrecking something.