1. Allowances are not noegotiable, they are fixed for all. Salary is negotiable.

2.If you will be married on the day you start work then you should let them know that. If not, your status can be changed later on when and if you get married, it will take time to change, but it can be done.

3. You mention allowances taken from the book. In fact, anyone with less than 24 month contract is offered company accomodation and fully paid transportation. You will get no money. You will get to know this when you receive your final contract.  The reason for this is; the first 3 months you will spend in company "welcome accomodation", then for the remaining 9 months you will not be able to lease anything under 1 year. Hence you will stay in company accomodation for the rest of your contract.

You can ask to be offered  a 23 month contract, because you can say, it is rather risky to relocate just for 12 months. They will listen.

4. As you seem to have Middle Eastern or Asian roots, chances are that you will be renewed. Systems engineer, is that IT or instrumentation, in either case anything related to operation is needed.

5. 2-day interview, is to show you around the work place and the City. You will have to find out where your place of work is. It might not necessarily be Doha.

6. Is the salary good? that is a very personal thing, because you are not relocating just for the money, you have other personal reasons. In a nutshell, if you're currently employed, and if the offer is less than your 'gross' before taxes, then you should be asking for more. Good luck.