In the first body paragraph you can also mention that maybe the overall population has increased during mentioned 5 years and the increase of seafood consumption is based by this change in population. Thus comparing seafood consumption now and 5 years ago is not sufficient to draw a conclusion.
this itself weakens the chances of the new restaurant becoming popular since the food prepared in restaurants is generally not considered as healthful.
But argument also mentions that these families do not eat home-cooked meals, thus most probably they prefer go to some restaurants.
Had these two factors been the only contributing factor in the popularity and profit of the seafood restaurant, such restaurant would have come up by now.
I think this is not strong assumption. If there is no precedent of seafood restaurant, this does not necessarily means that new opened restaurant will fail.
Also I think you have better to mention what particular questions should the argument answer, after all the task requires " response in which you discuss what questions would need to be addressed"
Overall your essay is quite good one, you mentioned important fallacies.