Even if MH 616 is open for terminal check-in, on MH, you will only be able to check-in and print BPs at the departing city (if on a separate PNR to the first check-in city ie MEL). I tried to get an onward BP printed at KLIA for an onward MH flight (separate PNR) with a very tight transit to no avail - not at the check-in desks, kiosks nor Golden Lounge. Fortunately I had made an OLCI and had BPs. and no checked luggage.
MH OLCI opens 48 hours prior. You will get 2 options for the boarding passes - (1) send to email or iPhone and (2) print BPs. They are not exclusive so you can do both. Option (1) produces a QR code BP. If you have Android mobile not iPhone, send it to your email to print off or retrieve the email attachment for the QR code to scan at the departure gate. This is important in you case as your transit time is very tight, depending on QF35s punctuality as well. MH requires a stamp on the option (2) BP, which are the normal looking BPs with the barcode, for regional and international flights and you may not have time to do so at the transfer desk at T2. The stamp is not required for the option (1) QR code BP (don't know why but it is a blessing). Do still print off (to PDF if you do not require a hard copy) the option (2) BP in case you need to chase QF later for points/SC if you've entered your QFF# for the MH sector).
Regarding your checked luggage, just hope QF is willing to tag the bags through to KUL for you. In light of the tight schedule, they may not after September 1 because you are on different PNRs. SIN is normally very efficient with transit bags but 2 years ago, we did the same flights as you've booked but on 1 PNR with QF. QF35 was late getting in, we just made it to T2 for the MH flight but our bags didn't. KLIA lost luggage was a pain to deal with. Rang QF in MEL, lost luggage located our bags and we got them about 1am the next morning.
At SIN, even if your bags are not tagged through to KUL, go to the MH transfer desk at T2, give them you checked luggage receipt for the MEL-SIN flight and they will locate and transfer the bags for you. You don't have to physically collect the bags off the carousel to check them in again. If you make it to the transfer desk and get your luggage retagged before the 30 minutes gate closing deadline, MH might hold the flight for you. They seem to do that a lot.
Good luck.