To push someone over the edge is a figure of speech meaning to cause someone to be in a state of extreme emotional or mental distress. In this case, since they were actually talking about a death by jumping from the edge of a building(I assume it was a building), to use that figure of speech in a literal manner was in poor taste (disrespectful).

Carver told Wardle to make sure he saw(escorted) Rokeby Junior firmly(in an aggressive manner such as by grabbing his arm and walking him off of the premises/property rather than just asking him to leave.

The shell suit was basically a shiny tracksuit. Definition on internet: A descendant of the tracksuit, the shell suit, which arrived in the late 1980s, was popular with the hip hop and breakdancing scene of the era. They were manufactured from a mix of cellulose triacetate and polyester making them shiny on the outside, with distinctive combinations of colours.

It means that everyone has their own motives and reasons for doing things. Sometimes it may seem like they are being helpful but they are really only out for their own best interests. Good answer found on yahoo:-)

A description of Landry's eyes (pale) between his light colored eye lashes. There was probably a description of his physical appearance earlier; he probably has white or blonde hair and his eye lashes are light in color also.

Yvette had a tendency to choose things in life which were not always easy or pleasant for her. I take it to mean that she usually chose the difficult path in life; her choice of Alec in this instance.

I don't know anything about the two characters here, but I would say that Strike asked the question and he could see all expression in Laundry's face disappearing---imagine a friendly face suddenly changing to a face showing no emotion.

I agree..I would say it meant that he suddenly became distant and disengaged from the speaker.