Honestly, in my opinion, the BP calculators are not very good for analyzing a deal this size. That being said I think you need to double check all of your inputs. I don't see any utility cost listed, depending on the area of the country sewer and water can be a killer. For the taxes you should make sure it is the amount that the taxes will be after purchase rather than the amount that the current owner pays, I've seen times where the taxes double or more shortly after a purchase.
I think if you are going to be analyzing deals this size you should either invest in a calculator specifically designed for larger deals or make one yourself if you are capable. There are a number of really good ones out there for a decent price. Also, if you are looking to syndicate this deal there is going to be a lot of costs that the BP calculators cannot do.
Fully agree with Mack, the online calculator is great for single-family properties and small multi-families but it is less adapted to large multi-unit buildings. You can find great resources online, including more advanced spreadsheets that will better assist you in your analysis. Feel free to reach out if you want more guidance. And best of luck with your project!