As the Gemarah here implies, it is unlikely that R' Akiva himself is the one who was 'matir' the neder, as he was 'noge'ah b'davar'. Moreover, the Gemarah in Ksubos, which brings a slightly diffent version, is explained by one of the mefarshim to mean that Kalba Sa'vuah then went to someone else to officially be matir the neder. Alternatively, as the Meiri suggest, KS made his own possesions forbidden to himself, and that is what he needed to be matir, making Rabbi Akiva impartial (incidentally, the father still must have refused to support his daughter and son in law, which explains their limited means for the first 24 years, or so, of their marriage.)
Either way, the pshat on the point by point summary should reflect this.
Kol tuv and Yashar Kochachem
Yonatan M, Toronto, Canada
The Beis Yosef disagrees, and says that the text in the Yerushalmi must be different. The Taz disagrees with the Beis Yosef.
You did not say how our Gemara implies that R. Akiva did not "Matir" the Neder himself. The Lashon "Asa (he came)" to permit his Neder (as opposed to Azal, he went) connotes to me that he asked R. Akiva to permit it. The Gemara in Kesuvos surely connotes that R. Akiva permitted it (he asked him if he vowed with this intent...) The Re'em here (in Shitah Mekubetzes) says that there were other Chachamim in his city who could have permitted it, just Kalba Savu'ah did not regret until now. The Re'em surely understood that R. Akiva permitted it!
In summary, Mefarshim argue about this. In my opinion the Gemara is Mashma that R. Akiva permitted it; those who disagree have other sources, e.g. the Yerushalmi.