Get the facts straight, its 3 of 120% in beginning of the battle + 2 of 120% each hit that has Hiccup Ignite. And if it apply the Ignite on same unit, it will only count 1. Not 2 stacks of 120% ignite on same slot.
Hiccup Ignite Dmg is indeed very high but it still has limitations not unlimited. Need to be precise.
Also the bonus Ignite from Jett is a multiplier not addition. Don't add it like that. So most your number are wrong.