1)Accomodation Cost- this depends on the area. if you will be given an initial accomodation for a month by your company, that will be great and enough time to find an area that suits your budget. If your package is 6k, and the housing allowance is included, check how much the housing allowance is, and then the area you want to live (that must be near or favorable to your workplace/where your children will study, etc.);
2)Cost of Fooding - there's a lot of discussions here on food- check Cost of Living in Riyadh from Everyday Life room- generally though, since I eat Indian food once in a while, it's actually cheap! A whole roasted chicken would only cost 20riyals from Indian restos and curry meat is within the same range as well. Vegetables/fruits are generally cheap specially in Indian markets near Indian communities (ranging from 5sar to 15sar per kilo).
3)Cost of schooling for std.6 and Std.2 student at Indian School- this I cannot answer, but for Filipino international schools (just to give you an idea), range of schooling is between 500sar to 1500sar per month for each child. It will be lowered down significantly if your wife decides to be a staff in the school, etc.
4)Transport and Medical Cost- normally shouldered by employer, but to give you an idea, 10SAR of limosine/taxi/cab can bring you up to 15 kilometers already, specially if you are friendly to mostly Indian and Pakistan drivers. Bangladesh drivers though are the best, since they rarely complain on whatever taxi/cab pay you say... Btw, in contrast to where I came from, taxis here rarely use the meter... it's always a pre-agreed amount...
5)If I go initially then when can I get my IQMA- depends on your company if they are quick.... but it should not last to more than 2 weeks.
6)When can I sponsor my family ( at the above salary can I
sponsor)- the trick is it doesn't depend on your salary... even if you are paid 200k SAR a month, but your iqama says you are a laborer (depending on the available visa), then you can't sponsor your family... visit visa and family status visa depends on the iqama profession, NOT ON SALARY.
7)Can my wife along with 2 sons join me later or is she not
allowed to fly alone- so your wife can fly.. just kidding... she can fly alone, your son alone, or all of them in one time... depends on your budget and if ofcourse, if they are granted visa your sons though, for sure, cannot travel alone, they are minors
8)Other rules and regulations for Indian family at Riyadh- please check the site.. .you'll be amazed that these questions were already discusssed
9)Living and dos and donts at Riyadh- the site also has these...