i actually wonder if your DS' reactions aren't MORE emotionally appropriate than his peers. it may all hit him a bit harder because he has the scope to really see the true horror and sadness of these things.
i know that's not totally helpful, because it doesn't actively help him move through the emotions to a place where he can manage them, but perhaps really validating his viewpoint might help him get a bit more comfortable with it? it's wonderful that he's expressing these fears to you - and keeping the conversation open will probably go a long way to working through the anxiety.
as a next step beyond validation, i wonder if maybe talking about the resources that people draw upon in times of turmoil might not help? it sounds like the uncertainty of it all is really bothering your son, and that's actually totally natural. but every day, ordinary people live through and transcend horrific tragedies - so perhaps thinking a bit about how communities band together and survive might be a good way to process the anxieties?
i have a very emotional husband, and i've found that helping him really walk around inside his anxiety and see his fears from different angles helps him find perspective. given how many years my husband lived like that with no help from his family, i do have to say that your son is very lucky to have you!
