The Seer of Veracity from Cho's Manifesto (Cross in loveheart with eyes) reminds me of some of the symbology of Dylan Klebold, The Hearts and Crosses .etc. It may have been influenced by Dylan Klebold in some ways who knows.
I believe Cho regarded the event for the fact that it was the first wideknown event of the sort amid the 21st century that he related to and may have seen televised reports on the event around the time it happened not to mention he wrote about recreating it around the time of its happening. As you said it is reported that Cho was asked if he knew about the term Trenchcoat Mafia and he said that he didn't, if this is true and Cho was being honest then it shows that he did not have extensive knowledge about Columbine except the brief outline of the event. He mentions Eric and Dylan entitling them martyrs and says something about something being done to them and that's about it as far as I'm aware. The backwards cap may be a blatant reference to Eric and Dylans likeness also.