Both of these phrases mean basically the same thing. If you need to, you can combine them in your translation. Alternate translation: "when the Jews trespassed, the result was that God abundantly blessed the non-Jews" (See: [[rc://en/ta/man/translate/figs-doublet]])
This can be translated as a statement. The words "their fulfillment" refer to either 1) the time when God blesses the Jews 2) when the Jews believe in Jesus. Alternate translation: "their fulfillment will be much greater." or "how much better will it be for the non-Jews when all the Jews believe in Jesus?" or "how much better will it be for the non-Jews when God fully blesses the Jews?"