Do homunculus receive the double xp as well? Don;t want to waste my time training it if he won't receive double xp as well
I'm pretty sure they do, why wouldn't they? Monsters, as a whole, give two times as many EXP. Who exactly gets those, whether it's you, your homun, or no one because the monster self-destructed, doesn't really matter.
It's not like your homunculus gets any different EXP than players do, except for MVP rewards, which are awarded to the homunculus' owner even if all the damage was done/received by their homunculus.