Interesting viewpoint, mine are mostly the opposite:
Myth 1: terrorism is homegrown: your proof just looks at the patsy carrying out the act - who has influenced and indoctrinated this person?
Myth 2: immigrants not a threat: I don't believe most are, but your study compares 2 equal socioeconomic neighbourhoods, which sounds fair but skews the final conclusion by design (transitionally poor due to recent immigration vs poor due to life circumstance, poor choices, etc)
Myth 3: Don't ban Muslims: your argument amounts to "can't win, why try?" - not very compelling
Myth 4: Terrorism is serious: yes it is, but the amount of attention it receives compared to other criminal aspects of society is disproportionate. I don't walk alone at night in some areas of the city because the danger is very real (backed by stats).  I did not think twice about attending Canada Day celebrations on Parliment Hill, even though some of my friends stayed away because of the possibility of a terrorist attack.