I am sorry to hear that your boy got into things at home.
There are two answers to this question:
#1 - There is nothing in Fig Newtons that will cause toxicity or will make him sick from that standpoint.
#2 - Anytime a dog eats a large amount of something that they are not used to eating, it can cause some vomiting and diarrhea. This is not likely to become life threatening, but can be quite upsetting.
Here is a link to an article on how to manage vomiting and diarrhea if this occurs:
I hope this helps!
As always, if you have further questions or concerns, please don't hesitate to ask them using the "reply" function.