DPS-SIN seems to be the problem, as that's not Jetstar Australia. I don't know where you're at on segments, but I think you'll have to either backtrack to somewhere in Australia with QF service to SIN (SYD, BNE, MEL, PER) or take MH from DPS via KUL. QF is set to start SIN from DRW in December on QantasLink, (according to Wikipedia) but that's a long time from now, also not sure when your trip is.