Hey there! We are totally happy to have you ask this question here, but we generally ask that people don't do it with personally identifying information -- it would be totally fine to rephrase it without his actual name and leave out the photo with his name on it; you could even leave the unit photo. The unit identification and date should be plenty to get a good overview of the fighting around mid-September, and then you don't run the risk of inadvertently doxxing your family. You could either make a new post, or just edit this one.

Also, our Guide on Military Identification may be of use to you. It provides a number of different resources, including how to request service records from a number of national agencies around the world, as well as graphical aids to assist in deciphering rank, unit, and other forms of badges or insignia. While the users here may still be able to lend you more assistance, hopefully this will provide a good place to start!

Let me know when you repost or edit it, and I'll send out an alert to some users on our Panel of Historians who do WWI stuff.

Thank you!