I took this flight earlier this year and the plane was quite full though not 100%, there were a few seats free.
KLM is competitively priced on this route, so personally I would not spend 33,000 miles on the miles ticket unless all alternatives were similarly expensive?
In terms of standby, you'd be better off calling KL reservations, then call FB if a seat is available so that it can be priced up. I don't see the local airport staff being able to accomodate you with standby but this is Bali and the people are very service minded. Anything is possible. KL has a station manager in MNL but I am not sure about DPS.