I rang to try to establish that, as someone I know also has a flight in a few weeks.
The girl said 'sometimes we rebook on PR, sometimes on other airlines'. The last bit was what I wanted to hear, as given as my friend knows, its timetable is daily to SYD, 5x/weekly to MEL, if the latter's cancelled, you may wait two or more days. And what if the next flight has insufficient seating?
She didn't specify 'which other airlines'. I hope it isn't 5J.
Unfortunately I don't know anyone who could answer why the two or three A333s remain sitting in Philippines. If they were operating, there wouldn't be the problems we're seeing.
It's up to you but I would never try a same day international connection unless booked on the same PNR. PR's international flights have just switched to Terminal 1; I thgink JL uses that one as well, so in theory that makes transfers easier.