Hello!
I'm not familiar with the ARPG plugin... since you say if affects enemy stats, I'm assuming it uses the engine's Game_Enemy class, or at least extends it. With that in mind, if you have access to the script variable that holds the enemy data, you could probably call the "getLevel" function. For example, lets say there is some script call in ARPG that returns you the enemy object assigned to an event in the overworld... something like "arpg.getThisEnemy()"... then you would be able to just append the getLevel function after it: arpg.getThisEnemy().getLevel(). That would return you the current enemy level value.
Hope this helps solving your problem!
Let me know how it goes!