I think you took the right actions given the situation you were facing. You made sure he was safe and medically stable. You moved him to a location where he could rest and stayed with him until the flashback ended. It’s also important to acknowledge how lucky he was to have you by his side when the incident occurred. I’m sure your actions during what must have felt like a terrifying ordeal made him feel safe and protected.
There may be better techniques that you can use in the event he has another flashback. One technique in particular utilizes grounding exercises. These exercises focus on trying to get the individual out of their flashback by trying to bring them back to the present reality. For instance, this can be done by asking the person experiencing the flashbacks to say their name. If they are unable to say their name state it for them. You can also try stating the day, the month, and their physical location. For example “you’re in your living room.” PTSD experts also suggest that if the episode occurs in a dark room, open the drapes. Illumination and bright lights are encouraged over darkness. It might also be helpful to encourage the person to open their eyes. You can also request that the person look you in the eyes. This may be one way to get them out of their “trance” of dissociation.
PTSD experts also suggest trying to coax the individual having the flashback to name items in the room or the color of clothing they are wearing. Are they wearing jewelry? If so, ask if they can feel the ring on their finger or the necklace around their neck. The basic idea with grounding exercises is to state facts about reality as a way to bring them out of a flashback as soon and as smoothly as possible. A particularly helpful resource where you can learn more about these techniques and PTSD is a book by James Chu called Rebuilding Shattered Lives. Another good resource for PTSD is a blog called PTSD and Me. The author of the blog states that he is not a professional but the readers seem to feel that he accurately articulates his experiences with flashbacks and other symptoms of PTSD.
You should also continue to encourage your boyfriend to attend treatment. He needs to attend treatment. There are non-medicine based treatments for PTSD that are very effective. Please let him know that he doesn’t have to continue to suffer from his symptoms. There is help available and he should make an effort to get it. It would also be helpful to you educate yourself on PTSD since it seems that you’re, at least at this time, his primary caretaker. I hope this helps.