Official MCT (minimum connecting time) at MNL domestic to international is 2h. So at least from that point of view: bad idea. MCT is also calculated on 1 PNR and checked-through bags, which is obviously not the case. Also keep in mind that CX check-in counter closes at T-45 mins. And even with a flex ticket: there's still a caveat called "no show".
However, I would suggest to contact Amanpulo and ask. Aman airport staff in general can do magic but it depends also on the carrier you are booked on (ex: Amanjiwo can get you boarding passes on GA even before you arrive at JOG airport).
From a TA point of view: I would never book this kind of connection for a client on separate tickets.
Why not book the Amanpulo 14:30 flight and then connect to CX 902 (ETD 20:20)?