1)Yaakov will rise in the end (symbolized by grabbing Esav’s heel). This is of paramount importance. Also the name Yaakov (given by Hashem or Yitzchak) indicates that he will ‘trick’ Esav and take the bechora and the brachos, as Esav himself said later in the parsha. Agav, in future generations too, the goyim (esav) think they’re on top and controlling the yidden but in truth the yidden are taking the hashpaos from them. This is a deep subject.
2)Avimelech realized he may have violated the treaty by throwing Yitzchak out of Gerar. He therefore came to (renew or) reinforce the original treaty by saying how good he was. Palestinian faker. Also it is possible that the original treaty (that in fact included Avimelech’s children) was only with Avraham. Avimelech (the second, according to targum) came to add Yitzchak.