Yes they can as they're tuned into us and use that famous animal "sixth sense" to know when we're happy or sad,healthy or sick or just stressed out.That's why they make such great companions,as as they can comfort us, cheer us up or take part in a celebration.
Yes they can. That is why they now have service dogs for people with PTSD and anxiety problems. My cocker has been an amazing anchor for me is past years.
Yes dogs can
Yes they can because when I'm sick my dog wont leave my side but when I'm healthy he always is up and active and wanting to play
Dogs evolved with us and because of us. They are advanced mammals with the most complex social structure outside of primates. So, to a certain extent your dog " reads " you like a book and can do things, such as responding to the simplest feelings, with accurate responses.