For Monkey Island in general, "Gone" by Tokyo Police Club seems to fit in tone:
TOMI Chapter 4, The Police, "Bring on the Night"
-Kinda for the sense of uncertainty and a certain desire for closure on Guybrush's part (Though it happens with disastrous consequences)
TOMI Chapter 5, Rush, "Ghost Rider"
-A bit risky I know, but the sense of continuing to find hope even through the bleakest darkness seems to work well with the various demons (Both physical and emotional) that Guybrush has to grapple with in this chapter.
Anyhoo, lemme know what you think.