I don't think Belial will actually be stabbed a third time by Cortana; in the Ghosts of the Shadowhunter Market, Belial is still around (and if I remember correctly, he shouldn't be around for at least a hundred years if he gets stabbed) and Jem mentions some kind of debt Belial owes him that hasn't yet been paid. Maybe, Jem and the rest of the gang get rid of Belial by making a deal with him? He gets Cordelia out of her oath with Lilith and promises to go away, as long as they stop hunting him? Maybe this is why the Carstairs owe the Herondales?
There's absolutely no way James will die, simply because of the fact that Jace has the same birthmark that stretches back to Will. The only option that could allow for James to die and also for the birthmark to reach Jace would be if Tessa and Will had a third son, which is impossible to insert into the story at this point because we have seen Tessa in the modern day and heard many references to her and Will's children - - they only had two, never was another one mentioned. It also can't happen that James dies and then another child is adopted into the family and takes the Herondale name because that would logically mean that this adopted child did not inherit the birthmark and therefore neither did any of his descendants, including Jace. This would be a plot hole, considering that it's known for a fact that Jace has this birthmark and it was this birthmark that saved Jace's life and allowed Imogen Herondale to realize he was her grandson.
was the inquisitor corresponding with Tatiana lightwood? is that why he would want to burn a random letter and any other evidence he had that he had a vendetta against the lightwoods and herondales? ðŸ˜ðŸ˜ðŸ˜
somewhere off in the distance i can hear the herondales readying to battle the man behind this account