Is 850 OMR enough for a family with 3 children?

Is 850 OMR per month gross salary fair for a supervisor job in Muscat?
Hi All,
My husband has been there in Oman for almost 2 years now but he still hesitant to bring us his family there because he said we wouldn't be able to survive on 850 OMR a month because he would have to rent a 2 bedroom apartment, buy a car, and send our 3 kids to school there, which the eldest would be grade 8, middle child is grade 7 and the youngest would be in pre-school.
Now I have read previous threads regarding cost of living, the way I see it 850 OMR would be just enough but we wouldn't have anything left for savings. I told him to ask his company for an increase, he said he already did and was turned down because they said he is not doing well enough on his job. So he is now working as hard as he can working overtimes and almost no day off but he is still hesitant to ask for an increase on his salary afraid that he might be turned down and be disappointed again.
My question is, is 850 OMR per month gross salary fair or standard for a "head-of-a-department" (he handles more than 8 people)  job in a very popular or reputable national media/press company there in Muscat, Oman? My husband has almost 15 years of experience in his line of work. Before he left our country we had our own thriving business which earns almost the same on what he is earning now.  I told him to ask his colleagues, even the ones who has lower rank how much they are getting but, it seems nobody can give him straight answer.
This is the breakdown of his salary: Basic- 450 OMR, house/room allowance: 300, utility allowance: 25 and conveyance allowance: 100. Total of 850 OMR per month. The company don't provide house or a car as service transportation, considering his line of work that needs to be on a lot of places most of the time( they only reimburse him for transports cost every time he was sent out on an assignment).
Last year, before his one year contract expired he was made to signed, this time, another 2 years contract with them without any increase on his salary.
He said he wanted to resign but we cannot afford to pay back the 850 OMR furniture allowance which was given to him when he started working there but, as per company policy has to be refunded in full if he is going to resign in less than 4 years of work.
We barely save enough money since we have to pay our debts here also for the money used on processing his papers when he traveled there. Any advise would be greatly appreciated.