Complex Mob AI

Hello! I'll keep this brief. Im trying to figure out the variables and such when setting up a Mob's AI but there's a lot that seems to be there but doesn't actually work the way it intuitively should to me. 

Mainly in the Logic Variables. As an example, I want to do a thing When Mob Hurt, then add 1 to a "damage" value, then check if "damage" = a number, and if thats true then it does an event. Like Spawn zombies. I can see parts that logically seem like they can do this but most don't slot together and I can figure it out. 

Also is there any way to call values from the Mob? IE instead of messing with custom scores to keep up with it for Boss Fight staging, just do When Mob Hurt If Entity Health less than 30 do thing?