first thing you need to know is that he is the same person he has always been no matter what the diagnosis.

second though its tempting for loved ones to try and find answers to why someone behaves the way that they do, its best to leave the diagnosing and such to that persons own treatment providers and remain who and what you are, their loved one, best friend and other side of his relations couple. by trying to self diagnose him with DID or a dissociative disorder you may end up doing more harm to you, him and your relationship...

for example here in america black outs due to rage disqualifies someone as having Dissociative disorders and qualifies that person for another disorder called Intermittent Explosive Disorder.

another example in your post you stated he said he decided not to feel so he didnt feel. here in america this would disqualify a person for having a dissociative disorder. why because many religions, and some meditative practices and self hypnosis, and some cultures teach things like being able to block out emotions and feelings, not let them harm you.

my point is just because someone does these things doesnt mean we as their loved ones should be trying to label them as mentally ill.jumping on the diagnosis wagon can actually hurt someone.

my suggestion is not worry about his mental disorders, take care of your own mental and physical health and let him do the same for his, just be his girl or guy, friend, loved one. thats all you can really do.

and if at some point he wants you to be involved in his mental health he can invite you to attend his medical and mental health appointments where you will find out what is actual disorders are and how you can best support him.