Colo, just to throw it out there. The company will only cover 3 children in school. So as for your fourth child they will not cover their educational costs. So figure about 50,000 AED (I'm making the assumption that this is Primary and NOT secondary education - secondary will be more).
As a First Officer you'll probably be making (as a ball park figure) between 39,000 - 42,000 AED. So right off the bat, about between 4-6 weeks salary will be going towards your 4th childs' education.
4 Bedroom villa? Unless you are already financially stable are are not coming to Dubai for the money, I think it's safe to say that on roughly 40,000 AED a month having a 4 bedroom villa will be tight. a 4 bedroom villa at the entry level end will be 180,000+ (and I think my figures might still be a little out). A Ranches 3 bedroom Al Reem was going for 170k last time I checked. Eitherway, these figures are again above the FZ housing allowance - again leaving you to dip into your own pocket to fund the difference (not to mention the bills, housing fee etc, etc).
Safe to say, nothing has changed since your days in Doha. Money will still be coming out of your pocket.