It seems most likely that Edward married Elizabeth in the period 1719 to1724 for which Isleham parish registers do not seem to be available anywhere - presumably the originals have been lost.

There does not seem to be a baptism at Isleham of an Edward Rust prior to this period and with many baptisms of an Edward Rust in the vicinity at around the right time it is difficult to be sure which (if any) is the right one.