@Gmt900
A few points from my side on your question. As I see now, it is a cross over, as Pannalal has answered your questions. Still, I let my answer be here, so you have two views about it. I guess Pannalal does not mind about that.
1. You can. But the point is to make the profit on time decay. So if you have less time decay left in your options, your profit will be smaller and vice versa when you take options which are more out of the month, you will have more time decay left. But then the probability calculation will show up with other numbers, which are even more far out of the money.
2. As he told: It is build on probability (Bell Curve). Here we have Standard deviations. In the example shown by Pannalal, the long leg is on Stdv one and the short legs are under it, split to the 100 point strike levels given in Nifty.
3. VIX is an important number for the probability calculation. The whole strategy by itself should not be much affected by vola as long as you do not change or play with the different legs under certain circumstances.
4. Answer given by your self. If you want you also can leg in. Your choice.
5. Watch the market moves and watch the prices of the options which are involved in that trade. So you always know where your risk moves too. If you have shorts only on one side, you any way should understand the risk when doing so, other wise do not trade such ways.
6. Well, just do the credit spread with the long 6600 C and sell the 6500 C. Less risk and less profit. Or you go more far out of the money with the whole strategy or you add one more long leg by buying two 6600 C. You also can take out one leg during the trade to reduce risk or go more far out of the month and so on. Many ways.
7. Answer given in point one.
Finally: High probability not necessary means high risk. Why? How does this sound: A high probability to not be touched by the market
= Lower risk.
Take care / DanPickUp