That mockup looks really good already. If it’s somehow possible to have Finn say: “It’s the First Order” instead of only “First Order” it’d be much better though. And if that’s not possible, I agree RogueLeader’s idea of him only asking about Rey. There’s no real need for him to say anything else.
And I also agree that the happyness in the shots after the destruction of SKB has to be toned down. It could actually work to just remove all cockpit shots and simply show the X-Wings and the Falcon leave with some sad music in the background.
Also, here’s something else: Before I saw Hal’s mockups, I would have placed the destruction of Hosnian Prime even later into the movie, so that the SKB fires just before it itself gets destroyed. That’d be after Finn gets “knocked out” by Kylo and we’d then need to cut between the Resistance pilots attacking and the First Order command center where they count down. Then it’d end with Poe flying into the oscillator just as the SKB fires.
I like the idea of the Resistance being this close to saving the Republic, but just barely not managing to do so, but Hal’s proposed version probably flows more natural with the material we have.