> “taken together, they strongly indicate that Óðinn, although not exactly the same as the god that we know from the Nordic sources, has roots reaching far back in time, probably as early as the Indo-European era

A reader might be interested in Kris Creshaw's "The One-eyed god" which reiterates Odin's similarities with other Indo-european analogues, specifically Apollo and Vedic Rudra.

Indeed, much of the Odin's acts and characteristics find similarities in the deeds of Rudra or Indra in Vedic myth. The Vedics even had a conception of afterlife similar to Valhalla, where the most excellent people and fallen warriors reach Indra's realm, carried by Apsaras.

Indra is also god of sacred verse, "vipratamo kavinam", which is similar to odin mastering the runes, giving a dual priest-king and warrior king function.

The efficacy of "several great deeds" is emphasized for both. Eg: The Havāmal: "140. word following word, I found me words, deed following deed, I wrought deeds.". The Rig Veda (1.101.4) - Praised, he is firm at every deed of his.