1. Since your wife never lived in USA in 2016 and she did not have an ITIN number I don't think you can file jointly, but I am not one hundred percent. Try to answer the questions asked by turbo tax, I remember turbotax asks if you are married and if you and your wife lived in US. Just answer them and let Turbotax decide how to file if possible.
2. I think you will get child tax credit since you are supporting your child financially even though they are in India.
3. I took my wife to the Social Security office in 2001 (at that time I was on H1B visa and she just entered US on H4 visa). She applied for her ITIN card at the social security office. It took us a few weeks to get the card delivered to us by mail.
