For form specific inquiries such as these, a consultation is needed.

The cosignor must be a USC or LPR to sponsor.

Yes the tourist visa may be revoked with IR5 denial.

Refer to your adjusted gross income for I864 purposes.

No it is not compulsory and you can adjust upon entry.

Best to follow up with NVC in July.

If the I539 was timely and properly filed, the applicant may remain until a decision is made.

He can make a request for 6 months but unlikely if he was only given 30 days.

You may travel while the case is pending and can update your travel at time of interview.

It will likely take 6-8 months for processing post submission.