1. I have tried this recipe thrice before posting it and the second time I made it was the best in terms of taste, however, in terms of appearance the cookies didn't crack on top. I would say, refrain from using beyond 150 grams of maida if you like melt in the mouth kind of cookies. But if you like your cookies to have a bite (slightly hard base) then add the additional 2 tablespoons of maida (or a little sprinkling of it until you are able to form a proper dough)
2. Since I was specifically asked to use sugar powder (granulated sugar measured and then powdered in the dry jar of the mixie) I stuck to the same. I have seen many recipes asking for the use of powdered sugar which in US jargon refers to icing sugar (also called as confectioner's sugar). Do note that icing sugar contains cornstarch (cornflour as we say in India) that acts as a stabilizer while the icing is applied to cakes etc. You could substitute the sugar powder with icing sugar to simplify things but I am not sure of the results.
3. If you don't like very sweet nankhatais just reduce the sugar by 10 grams (use 90 grams sugar for 150 grams maida). Since you will not know how the dough will turn out until you mix the ingredients together I suggest you hold back around 10 grams of the sugar powder and add it only after you have mixed in the additional 2 tablespoons of maida (if required). This is just a minor act of balancing the sweetness.
4. Traditionally nankhatais have cracks on top and hollow inside however there are many variations to this and by all means you can make the ones that don't crack up on top. No matter what they taste delicious!
5. When powdered, 1/2 cup of granulated sugar results in approx 3/4th cup of sugar powder.