first - she looks her age or easily younger..., second - being eye candy is not enough (she is beautiful woman in my opinion), beging good at acting is way more important
I know the actor will have guest role at best, but I think him saying "Su Ho" in the trailer can indicate that he will wake up from the coma in the end, I would be content even with phone call "He woke up", you know. Let's see. Anyway, excited!
even if Gwansik dies, even if others die it won't be a sad or open ending. Because that's how the real world works,…
I think almost certainly Gwanshik died first and she dies (likely) shortly after, and in the end they reunite in "heaven". The kids dying is extremely unlikely.