I don't know if anyone noticed but FN2187 is Finn. Can anybody remember what cell Princess Leia was held in in ep4? That's right, cell number 2187.
Kylo Ren's saber is, realistically, not meant for defence as shown when he pushes the extra bits into Finn's shoulder.
Hiding critical data in a droid? That's new.
Also someone needs to do me a family tree at the moment, this is getting into Egyptian levels of family tree shape.
So Kylo is Han and Leia's son. Rey is Luke and an unknown lady's daughter. I would say Rey is born of the Force, but she has flashbacks of her mother being torn from her, and the idea of Luke carrying a child to term while staying off the radar is... well..
That makes Kylo and Rey... cousins?
There was a book released the day before Force Awakens was released which gave us some insight to TR-8R. Finn was in a four person fireteam consisting of himself, FN2187, A guy called Slips, FN2003, so called because he always slips up. Finn would help Slip from all these slip-ups and it is likely that Slips is the stormtrooper who puts the blood on his helmet at the start. The other two members of the fireteam, FN 2199 and FN2000, or Nines and Zero respectively. Finn was the only one without a name because he was the leader of the small group.
Finn scored in the top 1% of stormtrooper tests and it was his caring of Slip that held him back. Phasma holds Finn back because of slip. When Slip dies at the start of ep7, it is the final straw for him, causing him to betray the First Order. Who else but either Nines or Zero knows him out of armor? Although canon ends before I even said Slips was the dead guy. So everything since then is speculation.
Nines or Zero probably made it their personal mission to find Finn and bring him back alive, hence the (possibly) non-lethal weapon used because of all the good times, but also wanted him punished for betraying them. It is possible Nine and Zero then BOTH trained to be riot control stormtroopers, but only one of them was able to confront Finn.
On a similar point, STORMTROOPERS CAN HIT SOMETHING IN THE GENERAL VICINITY OF WHERE THEY AIM!