I've played some dungeon crawlers, the sheer amount of content of some of them is plain scaring from the dev point of view, what most (If not all) devs do is to have small milestones, this keeps the moral up. For what I see you should even start with a lower count of monsters, have a minimum viable product and after that continue adding up more and more! I'm willing to bet there's still a lot you are trying to figure out for this game, so is better to redo a tiny amount of units and tiles than having to redo everything because you figured out better ways.