As an afterthought, there was a huge number of unused components in your original model, which was probably the reason for the dramatic file size decrease when unused were purged. Is it possible that you made components of some of the missing parts and then accidentally deleted the only instance in the model? If you do that, the visible instance in the model will be gone, but the component’s definition will remain in the model. I don’t know what the missing parts were supposed to look like, but there are unused components in the model that could conceivably have been floors and walls.
And another recommendation for good modeling practice: don’t bring component definitions into your model unless/until you are planning to use them. Especially if they have detailed geometry, they will bloat the model file without contributing anything.