Actually I have taken credit for a similar deal in the $4MM range a few years ago. No, the landlords statement will not be acceptable on income levels. What you need to do instead is get the college to provide you with their student income break up. Work with their community relations staff and they should be able to pull this together in a heart beat. (They do so for many goverment programs so it's information at their fingertip). If they can show that the majority of the students are LMI (which is not uncommon unless it's Harvard)

you should be fine. Follow then the fair market guidelines, and document that the rooms are built for apartment sharing. (That landlord statement is perfect). EXCEPT I'd want to document the percentage who are students and the percentage who are "young professionals" which could mean wealthier folks. With a $600 average, you're still ok either way because they're below market, BUT you then must discuss proximity to the college and the landlords attempts to meet this market need.
I'd also cover the rent disparity. Why are some $600 and some $900? I'd probably take a partial credit for the loan given this and assume the higher rents were going to the professionals and the lower to the students.
Fair market rents is not the only factor by the way. You can also use average income for the tract and a percentage of that income that could reasonable go to housing. It's a more generous figure than fair market rents quite often.