We can do this speedrun? because the XP boost never will end

it is impossible until the "temporary" xp boost ends

Ok

The boss spawns as you reach the xp goal, so theres no way to purposely balance it by getting more xp since it force spawns unlike the skill levels itself where you can choose when you take advantage off leveling up (accesing the bazaar, another island ect.) so you can get more xp to makeup for the xp boost before triggering the launch pad or bazaar