Very nice. [:)]
Feel free to submit your code as an attachment of a feature request.

There's no direct method to get the wall which windows and doors are attached to.
Don't be misled by the isBoundToWall method: it tells if a door or window was dropped on a wall last time it was moved, and is used just to adjust resizing behavior of doors and windows.
Holes in walls are computed in the createWallGeometries method of Wall3D class, but you probably saw that already.