I'm running a game myself and I've changed up some of the words used for some concepts to cut out ambiguity. Instead of Bonus Damage I use "Enhanced Damage" because Bonus Damage just allows you to adjust the regular damage roll. With the word "Bonus Damage" you'd imagine it is the same as Critical Damage, but it isn't. At the moment I'm unsure of if it stacks, I'd have to check but I'd assume so.