Correct - there is no DL award on SQ metal to SYD. You could fly to SIN on SQ with DL miles, then purchase a ticket from SIN-SYD. Before you do this, check your map.

If you drew a line from HNL's meridian to SIN's meridian, you'd find SYD roughly halfway in between. Asia is not a logical connection to SYD from the US. SIN is 4,000 miles away from SYD (more than JFK-CDG) - it's not "in the neighborhood."

Routing from the US on anything other than UA or QF/AA's nonstops out of LAX/SFO will cost you at least a dozen incremental hours (once you include stops). Unless you have time to kill and would like to see SIN or ICN, these routings will cost you a lot of time.