Smallfry

At that moment she may not have been but in the future who knows

Shang's words "There was no other name I could use", simply isn't true, for example, my name might be Bob, but Bob isn't the only name I can use, making what he said a lie.

The weird thing is they specifically state that training your mind trains your reaction speed later in the story.

No, my point is that Shang isn't the only name he could've used, it's the one he chose to use.

Yep, not cold-blooded even though his thought process was "I should've killed them all".

Suddenly trust her for no reason, cool. Clearly a smart dude.

Isn't he just passing through, why would it matter if she like him? Also she's weak, he could easily surpass her in a month or two, there's effectively no point in becoming friends with her.

What else were they supposed to threaten him with? It's not like tasers exist in that world.

Except he has lied already, for example, "There was no other name I could use" a lie, Shang was not the only name he could use, Alex was an option, but the God decided not to use it.

That doesn't make too much sense, dince training your mind would train your reaction time as well.