I didn't like how all the system was done, so I just remade it for you (Taking into consideration that you want all of it in just 1 table):
Add to your data/global.lua:
monsterSystem = {
[1] = {name = "rat", pos = Position(1000, 1000, 7), expReward = 5000, goldReward = 1000},
[2] =...