I think I can explain at least the first one.
The grandpa is very religious, (tells the boy to come down, as he is mocking the angels) and I would have guessed that this was his way of telling the boy that she was dead. Now, I haven't listened to the story in about 3 days, so correct me if I am wrong on this one. We learn (again... I could be wrong) that she went while jumping off the roof, and the grandpa says that she never came down. He could be referring to his belief that she must have gone to heaven, as she was to good to go to hell.
Adults also usually try to comfort children by saying things like this when somebody close to them, or a pet, dies.
As for b), I think that the grandpa might be just completely shaken, and realizes how he has been treating the boy. After this incident, he buys the space-ship model, and starts to change his ways.
So far, I think that this is the first EP story which really got me wondering about what happened at the end. Sure there were others, but I just signed up to a forum to discuss it gorramit!