Does "malefic rune", possible typo from "tune" in the context?

Rune is correct. It is used in a figurative sense - a flowing stream

OED:

3. A flow of water; a stream, a watercourse. English regional (chiefly south-western) in later use. Cf. rean n., rhine n.3

OE Aldhelm Glosses (Brussels 1650) in L. Goossens Old Eng. Glosses of MS Brussels, Royal Libr. 1650 (1974) 186 Perpes aquęductuum decursus : singal renes [read rene] wætertige.

1849 W. A. Williamson Local Etymol. 96 Rune, a watercourse, a channel, from the Teut. rhennen, to run, flow.

It is a very old and rare word.

(You can hear it spoken at about 6:49 in ""The Feast in the Abbey" by Robert Bloch / A HorrorBabble Production"" at https://www.youtube.com/watch?v=eAf2-99Y0II