My point was that Arthur was asleep in the van; the weightlessness still affected his dream. The weightlessness in Arthur's dream still affected Eames while he was asleep, so it should have affected his dream and the weightlessness should have been there under that theory.The van falling in the 1st level either caused the absence of gravity in the 2nd level or it didn't. I think you're saying that it didn't but my interpretation is that it did. Otherwise it's difficult explaining why gravity exists in the 1st and 3rd levels but not the 2nd, and I don't think the deterioration theory explains satisfactorily this skip in gravity.
I'll try to clarify my position:
1. The 2nd dream level is hosted by Arthur, designed by Ariadne and populated by Fischer's projections.
2. Arthur's body in the 1st level is experiencing a weightlessness because he is seated inside the falling van.
3. This experience of weightless does exist in real life, as seen by astronauts who train for zero gravity by floating inside jet planes which have been put into a temporary nosedive.
4. This weightlessness sensation translates to a lack of gravity inside the 2nd level.
5. The lack of gravity does not occur inside the 3rd level because this level is hosted by the sleeping Eames in the 2nd level.
6. Though Eames is sleeping in a zero gravity situation he is lying completely still, the sensation he experience is no different from him lying on a solid bed.
7. Because a motionless Eames doesn't actually experience weightlessness as opposed to the falling Arthur, gravity still exists in the 3rd level.
The dream-within-a-dream must have some kind of automatic suppresser to break the chain.