The status_code: 403 bit in the response shows you that the issue there is authentication. AWS should return 403 when you’re authenticated but you don’t have access to the resource you’re requesting (the AWS bucket in this case).
Can you list the objects in the bucket by using awscli?
Not sure I follow, I’m sorry. I’d recommend making sure authentication is right and that you can access files with awscli. If that doesn’t work, then the problem would likely not be ExAws, but indeed credentials.