It looks like you will have to pay:
1. Another 500 OR -750 OR for a nice 3 bedroom villa (Allowance is 590 OR).
2. Another 150-200 OR a month per child for schooling costs at an expat school. Allowance is 75% upto 1800OR/yr depending on age/grade. Fees run around 3300OR plus deposits.
The first year is probably catch up. After year 1 I think you might be able to save. Definitely more than you would be able to in Dubai working for FlyD.
I am not as yet in Muscat--anyone in the field care to agree/disagree?