The first choice, "<span>I suspect that he would enjoy living with whales more than [he enjoys living with] us." is the correct one. Remember that elliptical clauses are sentences that are missing part of the clause and needs to be completed with a correct pronoun. In this case, the correct pronoun is "us".
The author uses precise numbers implying he has done his research and knows what he is saying, and his use of vocabulary suggests he is educated on the subject and knows what he is talking about.
