QR 6500 housing is a bit too thin with the prices in Doha. Maybe you could talk your employer in providing accommodation instead. With QR 6500 the best you can get is a 2 bedroom semi furnished place, not in the best of areas.
School fees are insane also. If you consider sending your son to school you should inquire about school fees allowance.
A new 4x4 will cost around QR 100K. The good ones are around QR150K and up, and lower end is QR 90K - 110K.