Is my backing out of an agreement with my friend to complete a study project, due to my fears of his inability to succeed and his slowness, considered a betrayal of a promise or hypocrisy, especially since the agreement was not a covenant or an oath?

There is no sin upon you for backing out of completing the study project with your friend. Fulfilling a promise is highly recommended (mustahabb) but not obligatory (wajib) according to the majority of scholars. The warning mentioned in the noble Hadith applies to those who habitually engage in such traits.