If I have approx 3 o'douls on Saturday. And am done drinking at midnight, will I pass an EtG test at 9 am on Monday?

There's not much research on NA beer but that existing would indicate you should be OK at any period beyond 24 hours. Based on amount consumed.

O'Douls, containing about .03 abv, will create EtG but such synthesis is rapidly eliminated. Probably EtG would not reach a detectable level or be below the cutoff or be completely eliminated at the time cited.

Very unlikely EtG would be positive but you are within a time range where detection is possible.

Cutoff 100 ng = detection unlikely
Cutoff 500 ng = very very unlikely

Ref:
Thierauf, 2010
Musshoff, 2010