SQ availability opens up at all sorts of weird and wonderful times so if you like the idea of it, keep an eye on availability. Waitlisting is good, but I've had availability open up and waitlists not clear so it's worth checkin once a week.
What ... angled beds
[The times ex-CBR are pretty coughpy considering length of flight. Even in J that's not going to be a joyous night in the sky, particularly with angle-flat beds in J.]
That said, my parents live a couple of hours out of CBR and for them, being able to get on a flight after work and wake up in SIN without any dom connection will be a dream come true – despite the bad timings and less than ideal (but still great) J product.
So I would absolutely second this. Spend that night in SIN, hit up a hawker centre and just enjoy the city's brilliant food. 20 minutes in a taxi the next morning and you're back on track.