Therapy to build communication skills and learn more about one another's disorders so you know how to effectively support one another.

Individual therapy may also help both of you so you guys can identify triggers and episodes before they happen so you can communicate when its happening/going to happen. That way both of you can prepare for whatever is going to come and be able to work through it. Therapy will give you that platform.

The last thing is helping him feel comfortable and letting him know that its OKAY to have triggers related to the PTSD. Learning about it and finding a therapist who has army experience/specializes in PTSD related to military experience will empower him to overcome the fear of shame that's coupled with "needing help." Try to get in contact with your local VA hospital and learn about support programs for their veterans. There may be groups, therapists, psychiatrists and other family-related groups that can help empower you and him to work through his PTSD. But remember to also get help for yourself and get your needs met too.