That looks less like a shuttle and more like a large missile. I don't think we've seen anything except missiles leave a trail in space before. It's also pretty long for a shuttle, which would be an odd design choice for Star Wars to make, I think. But it's a really weird angle for a missile; it's not pointed directly away from the ship, and it doesn't look like it's going backwards. We probably won't get a better look at it later either, unfortunately.

Skulking is a good word. And describes Poe's appearance quite well here. It looks like he's just slowly walking by the door without going inside. I bet if Poe's asked to go in to explain himself, and he's shown going off elsewhere instead, Jim's excuse is going to be something like "Even better! This is getting more fun all the time." or something like that.

And this all makes me really wonder what Poe's plan is in the movie. It seems like Finn and Rose have departed for Kanata's location, given the comic set-up. But that wouldn't explain why Poe was left behind. Does he have a different mission now? He doesn't look injured, so that can't be a reason. Maybe he really wants to fix up a new X-wing for himself? I guess I could see that, but that wouldn't make for a good extended movie scene. Not unless someone else shows up for a conversation, short or long, and unfortunately BB-8 wouldn't count. As a mascot astromech droid, I'm pretty sure he only speaks in Beep to mimic what Artoo had in the first six movies. Which would mean Poe would basically be talking to himself.