The temperature tracking feature is useful to anyone to allow you to anticipate illness. I check this daily and if you notice a significant temperature increase it could be an indication you are about to come down with something.

I have something like this also, but on me it looks more like a tan. I wonder if the green light these produce causes some melanin to migrate to that location in some people.

Just use a little dish soap in your sink. Wash it regularly and don’t wait till it gets gross.

Sounds like a great excuse to get a new watch! As far as being hacked, I think that is very unlikely. They would have to have a route to get into your watch which would probably be through your phone. Just don’t surf the porn sites on your watch and you’ll be fine. :)