I agree; it was a challenge to use up the available space, and I gave up by the time I got to the basement, which is enormous. Apparently the building was used as a married student dorm in the 20's.
What size lot is it on? I always love replicating real houses for the Sims and I find over sized rooms a huge challenge myself sometimes. I'm working on one house that is based off of an old family property that my father used to have, and it started out taking up 40x60 lot. o.O; But I find if I lesson gaps between windows, or even cut out a bunch of windows I can greatly reduce the size of the house without sacrificing the overall appearance of a house.... If one wall actually has 20 windows in a row, 15 windows or even 10 in a row can sometimes still get the same point across. I managed to get it down to a 30x40 lot but I'm still trying to get it smaller...
I like the house though, and though I said the hallways were unnecessarily large, I can't be too critical because some houses I'm working on currently have empty hallways larger than that and I still haven't been able to find a way to fix them.