Any special obligations to shareholders - listing agreement

Question 1:
I am planning to write CPA exam this July. The application process might take close to 3.5 months. So if I need to write the exam in July is it ok to apply for Visa in May? is it too late? if so what is the ideal time before which I should apply?

Question 2:
This is a tricky thing... When I apply for my exam, I would be getting something called the NTS (Notice to Schedule). This NTS tells that I am eligible to sit for the exam within 18 months. Using this NTS, I need to apply for the individual exams and pay the fees for prometric centre where I should write the exam.
Now my question is, is it ok to apply for the visa with just the NTS? or should i necessarily pay the prometric centre fee and then only apply for the visa? It costs around $1200 to apply for the exam at prometric centre. Can i do this once my visa gets approved? or would the officer ask me for the prometric centre documents too?

Question 3:
What are the documents I should carry for the interview apart from the proof regarding my CPA exam?
The US consulate website talks about some sponsor letter... I am going to stay at one of my relatives place and give the exam. Should I get a letter from them? If so is there any format?

Is there anything else I should be concerned about?