Is reversing speaker polarity worse than listening off center?
Sound propagates at about 3 ms per meter.  440 Hz therefore has a wavelength of about 760 mm, which fits with what you said.

If you had two speakers pointing at each other and you were directly in line between them and they were both emitting the same 440 Hz signal, then you'd perceive nulls and peaks in the sound with apparent 380 mm (15 inch) repetition.

However, speakers in a normal listening environment aren't opposite each other, and they don't usually play a single frequency.  The pattern of apparent inversions is different for every frequency.  The distances between inversions are also larger when you are not directly in line between two speakers.

Therefore, in the general case, you can't compensate for the polarity of one speaker being flipped by moving the listening position a little bit.