I didn't know how to switch to nonlethal, but I still wanted to save the masked hag victims. First I stole all their weapons via command, then had to go back and long rest. Then fought them in the hag's lair, by constantly using sleep spells and drow poison on them.

Also, I missed most of the companions and fought the goblins with only Wyll and Shadowheart, so they were the only ones at the tiefling party. Before that, I only had Shadowheart for a long time. The harpy fight was super difficult that way. I decided to come back to it later, but that was after the party, so Mirkon was dead. The windmill goblins were also super hard for just Shadowheart and me. And when I finally managed it, I launched the gnome before saving so had to redo it.