“Difficult” doesn’t adequately describe what both of you are going through. It is hard for you to love someone who is this unpredictable. It is hard for your boyfriend to live in his own skin. I hope he is getting counseling services and medical treatment from your local VA. He deserves treatment and support to manage whatever diagnoses he is carrying. All of the diagnoses on the list are a big burden for the sufferer and often for the people around them.
My guess is that your boyfriend keeps saying “for now” because he is unable to see beyond getting through the immediate situation. That may have been a coping mechanism for him that worked while he was in active service and especially if he was in combat. It isn’t helpful in a relationship meant to be long term. One of the huge challenges for vets is that adapting to civilian life often includes having to stop using the very techniques that kept them going while in harms way.
Fortunately, there is good help available to treat those illnesses. But treatment only works if a person accepts and works with the treatment. The most helpful thing you can do is support your boyfriend in getting — and using — treatment.
Meanwhile, you can’t expect yourself to know how to support someone with mental illness on your own. Fortunately, there is often help available for family members of vets. Every branch of the service now recognizes that families (and significant others) also serve. If you are near a base, there may be a support group or support program available. Do check it out.
If you are not near services for vets, do consider looking into whether there is a chapter of NAMI (National Alliance on Mental Illness) near you. This organization provides information, education, and support programs for people with mental illness and their families. From their website: “NAMI Homefront is a class for families, caregivers and friends of military service members and veterans with mental health conditions. The course is designed specifically to help these families understand those challenges and improve their ability to support their service member or veteran.” Attending such classes also puts you in touch with others who are going through much the same thing, which allows for providing mutual support with people who really understand.
One more thing: One way out of a tug of war is to drop your end of the rope. There are only fights if both people agree to do it. You don’t have to accept invitations to fight. Instead, you can offer reassurance, ask what is wrong, and stay in a centered, mature place so you can partner with your boyfriend to identify solutions to the problems.
I wish you well.