Using subwoofer as a piece of furniture...

[Timn8ter]

It doesn't surprise me that much. For marketing reasons many designers try to come up with a smaller box. If you trust the parameters you're using then you're numbers are probably correct. But, when dealing with SAF, DIY designers have to come up with smaller boxes too.

[navin]

u can use aperiodic loading to reduce box size to some degree.

[Duo]

Well.... You could use a ton of Mu-Metal to protect the tv from magnetism, but that would probably be expensive and unstable since the vibration from the subwoofer might cause it to lose its magnetic shielding properties, which are obataind through the process of annealing.

As for vibration, yes, this will cause microphonic vibrations in the tube and distort the picture visually if the vibrations are great enough. I've done this without the sub or speakers even near the tv and in that case it's unavoidable without removing the tv. Though, the vibrations occurred for over a year of listening and never caused a problem with the tv.

And aperiodic loading, I might add is something I've grown to like.
It can really make a small box seem big to the right driver. I have a driver with a VAS of over 300L and the aperiodic measures of the cabinet let me have a smaller one.