(1) SAVE AS I SAVE - from SAW IV
(2) Amanda, John's chosen disciple, developed into a Pontius Pilate-type character, eventually betraying John.
(3) John's madness began after his wife was killed, who was carrying his unborn son.  A sacrifice, like Christ?  So that John could purify those unworthy of life through his games?
(4) John, in his own twisted way, tries to teach people that vengeance and hatred only lead to unsavory ends.
(5) In SAW IV - On his death-bed, John asks for forgiveness from the man he knows will murder him, all the time knowing that this man's lack of forgiveness will have dire consequences.  (Jigsaw is killed by this man and flat-lines, and thanks to BlueTooth, this guys wife's head splatters all over the wall.)