1)
What is the meaning of "Alai Elokim Nedarecha"?
1.
Radak: It is upon me to pay the Nedarim that I made to You during my exile.
2.
Malbim: Hashem's promise via a Navi is like a Neder that He must fulfill. There were two such promises - of kingship, via Shmuel, and that he will return to Eretz Yisrael, via Gad.
2)
How will he pay "Todos"?
1.
Radak: These are Korbanos Todah via which one thanks Hashem when he is saved from affliction.
2.
Malbim: Like You vowed for me, so I will pay You (like verse 14 explains).
3.
Shocher Tov (100:4): All Korbanos and Tefilos will be Batel in the future, except for Korban Todah and thanks will not be Batel - "Todos" refers to Korbanos and to and Tefilos [of thanks].
