I think as Poe and Rey are talking we see several shots of either closeups or tight medium shots. So there’s plenty of time for Finn to walk up. I think it’s better this way than lightspeed skipping dialogue that doesn’t make sense if the TIEs don’t follow them into hyperspace. The only other way is to leave the scene untouched and to assume the term refers to jumping to lightspeed either through the ice or without calculations.

The horses arriving is a little abrupt but has to be that way to remove the compass. I tried to have “Head’s up” during the shot of Rey looking toward the DS but we decided it was more important to have a Sith whisper in that moment.