Tranz says "Tess unlocked your would-be assassin's phone". That is a past event and the said assassin is dead, so "would-be assassin" is not correct. "would-have-been assassin" seems correct.
Dylan says "What kind of misunderstanding gets your mother arrested by her alleged boyfriend and ..." That is a peculiar use of "alleged". The crux of alleged comes when the person it is said about denies it. But, Dylan has already said twice that Zoe's mother and Dylan's father were dating, and Grace has told that to Zoe, thus, it appears to be an established and well known fact, and Harris has does nothing to indicate that he intends to deny it. "alleged" is not correct in this use.