Earlier, Bigon said that one trillionth of a gram of Monarch's poison could reduce her to the size of a grain of salt. However, when Monarch was hit with the entire poison (which somehow didn't affect anyone else nearby, not even a splash, and didn't hang around in the air either for that matter), Monarch was MUCH bigger than "a grain of salt". More like the size of a salt shaker.
In the past when the Doctor put himself into a trance to eliminate the need for oxygen (Terror of the Zygons), he stopped breathing completely; he didn't start breathing harder, which also is not a "trance".
The Doctor using the cricket ball's momentum to propel him towards the TARDIS is quite preposterous. Firstly, for him to be able to throw it with such precision in a zero gravity environment - and while almost succumbing to the effects of such extreme cold - is stretching credibility. Furthermore, even if he could have done that, he would not have been able to grab onto the side of the TARDIS nor would he have come to a stop. He would have either bounced off the TARDIS or shot right past it.