Seeking advice or guidance on helping partner with recurring nightmares

Hello r/hypnosis,

I'm a self-taught recreational erotic hypnotist who's only passingly aware of the content of this forum. I have no formal experience or training in proper hypnosis techniques, have very little knowledge of nomenclature past "induction" and a layperson's understanding of "trance." Now I'm seeking advice on something somewhat outside my wheelhouse/comfort-zone.

For background, in case any previous experience is relevant, I've been successfully doing hypnosis for about 4-5 years, mostly on my current partner, and used hypnosis for both therapy and dream inception, successfully. I've only ever done hypnosis online, almost exclusively through text, but some over a video call. I used to believe that hypnosis couldn't directly effect dreams because it's a state of consciousness, and dreams, in particular the dreams we remember upon waking, are only the most recent brain activity of the unconscious brain. Despite this, I hazarded to try anyway to use hypnosis on my extremely skilled and suggestable partner, to soaring success. I'm able to, in a trance or using subliminal messaging, describe a dream to him in an arbitrary amount of detail and suggest for him to ruminate on it while he falls asleep, when he wakes to turn in the night, and have clear memories of it in the morning, filling in any gaps as he "remembers" them. At first I thought this was only simulating the experience of piecing together fragmented pieces of a dream the following morning, but I have reason to believe he's actually having these dreams while asleep. They have very recognizable "dream logic", blend into other dreams, and are reportedly extremely vivid, even more so than our waking hypnotic escapades despite my not being there to continue the suggesting. We've used this almost exclusively for erotic recreation, but now I want to use it for something more supportive.

He was in a damaging accident early in his life and is a generally anxious person. He's also had vivid and viscerally painful nightmares for much of his life that have continued in his relationship with me. It's no surprise that some of his most despised nightmares are of driving. When I give him induced dreams, he almost never has nightmares on those nights. That's a primary reason I do it; to protect him. But now I'm looking for any advice to address the problem more directly. Is there anything I can use my amateur hypnosis skill and his ready suggestibility to help him? Barring the obvious approaches of seeking therapy or attempting to cure his underlying anxiety, both of which are outside our attainment, thus the post here.