Deflation on the sidelines would be in the presence of a lot of people. It would be possible, but I am not so sure it is the option that makes the most sense. It is the first time I have heard that theory, so I would again suggest that how you might approach the situation may not be how most others would approach it.

The same goes for your theory on measuring vs deflating. Also, there are clear references to a needle and deflation in the text messages.

As to the phones, it seems to me that Brady submitted the old phone in the hopes that the NFL would not realize that there was a missing phone. I think the timeline is such that he only owned up to the missing phone (and excuse) after he was caught because the examiner discovered the time gap.