Extra protein is good for you, as long as they're not poisonous. See if there is a hole in the bag or webs in it. If not, then it was probably on the bag in your pantry and crawled in when you opened it. A spiders gotta eat too, you know.
I think you can eat any spider.
Pretty sure digestive enzymes and acids will take care of destroying any dangerous goods inside said spider.
Most toxins found in stinging/biting creatures do their magic because they skip digestion and go immediately to bloodstream/tissue. Our stomach is a major defensive barrier.
Could be wrong on that, however. I don't think I am in regards to animal/insect toxins, but obviously there are toxins that can be delivered by food, survive the stomach's environment, and kill you. Of course, bacterial and mold toxins can also survive that journey. Well, the bacteria and mold can, not sure when/where they deliver toxins, might be after the stomach.