Lesson learned, unless you are a large and/or fat person, do NOT pay extra for the exit row seats. All of us large/fat people do just that. If you are relatively thin and fit pretty much ok in an airplane seat, then pay extra for the exit row, you better expect to sit next to someone like this. I fit better than that, but I still feel like a 14 year old crammed into a denny's child seat.
That said yes that guy needed an extra seat, maybe 2, but unfortunately there is no good way for them to gauge this, and very few people are going to admit to being like this and be forced to pay double for the same flight. Unless you come up with a mock-up of a seat and force people to sit in it the way they are supposed to put their carry-on luggage in those little cages to see if it will fit.