If the sleep spell is keeping you up at night, because of confusing mechanics or soft scaling, come take a look under the hood and sample two sleep spell solutions.
This is my dirtiest DM secret: I don't fudge dice. I fudge entire monsters. This DMing tip can help you manage the tide of combat to dramatic conclusions.
How do you run a sandbox without being completely overwhelmed by the expansiveness? Let's tackle this by dividing it into two sections: planning the sandbox and running the sandbox.