Size doesn't matter...
Very, very, VERY doubtful and pretty much impossible if you physically inspected/looked at the house prior to signing the lease, which is likely the case. There aren't any less bedrooms than there were when you inspected it. You're renting a residence. It isn't a commercial/industrial lease.
EDIT: Talk to the landlord. Print out your above post and show it to them. They might just allow you to cancel. I sure would consider it if I were them. Be prepared to offer them some compensation for their inconvenience.

