Answer
Yes! You need to cook it though. You could use it in a curry or a soup too. I always toast the seeds and sprinkle them in salad.
The "meat" can also be used in pumpkin bread, cookies, cakes.
I don't think that's sucha good idea, the pumpkin has been sitting out all day and accumulates bacteria and germs. It's best to use a fresh pumpkin and throw out the one ou used for the jack o lantern.