The odds of getting attacked are so low that you’re just being paranoid if you think guns are a necessity and that goes back to what I said, just like your attacker, what you need is help, not a weapon but you choose to want a weapon instead because it’s easier to deal with the trauma this way than to reflect on yourself and the society you live in and choose to encourage by arming yourself.
Also, good luck with your tueller drill, I hope you always keep people at least 20 feet from you (which is a very long distance to pull out a knife on someone!)
MythBusters covered the drill in the 2012 episode “Duel Dilemmas”. At 20 ft (6.1 m), the gun-wielder was able to shoot the charging knife attacker just as he reached the shooter. At shorter distances the knife wielder was always able to stab prior to being shot.[5]