I have spent lots of nights in SG over the years, albeit none since the pandemic! And nobody asked but here's my opinion:
Public Transit: While I love public transit and it's often faster than driving, in SG at your hours (Sat night and Sun AM) it will be very fast to the airport from any of the hotels. Take a taxi.
Also if the inbound flight is late at all, you may miss the last train around 11:45PM or midnight (?)
Are you flying SQ J on Sunday morning? I'd not worry much about hotel breakfast since SQ biz lounge late morning should have some decent options.
When Hawker Centres are open late, someone may have mentioned that not all of the stalls are open; it could be just a handful, so keep expectations realistic.
I agree with using a 35K certificate in SG vs. paying for a night with another brand in expensive Singapore-- because I remember when crappy love hotels in Singapore started selling rooms as normal hotel rooms 10+ years ago, and even those go for US$100+! See Ibis Budget hotels in SG if you don't believe me.
If you were in KL or Jakarta, I'd splurge and pay out of pocket money for a lovely 5* hotel for the same price as a SG love hotel.