The DS260 only needs to be filled in for derivatives who want visas so Tony is incorrect. Cashes as I understand has filled in on his DS260 that he has a wife who will follow later, which is fine.
Cashes, you are correct to bring evidence to prove a real relationship because it will maybe look suspicious a little that your wife is not coming, although it is also not that unusual for a husband to go first and find a job and place to live before the wife joins. It is understandable that your wife would not want to leave a sick parent. Take all your evidence and be honest in your answers to the CO.