A lot of people with CH are negative in the sense I think you are using it -- resistant to things that we "outsiders" think might help them. I include myself as an outsider because I don't have CH, my daughter does. My daughter was so mad at me as I was going about getting a proper oxygen system set up for her! She had "tried" oxygen with a very ineffective system, concluded that oxygen didn't work for her, and didn't want anything more to do with it. The new system works great and probably helped save her life, along with other ideas from here, but it's my belief that many people with CH have been so disappointed by things that they hoped would work but didn't that they would rather avoid having that disappointment again than try something else. It wouldn't be surprising if your partner has had bad or inadequate advice from doctors (as I mentioned, it doesn't look like he was prescribed any preventive) and probably way too much "I get headaches, too, and here's what I do ..." input from well-intentioned people who have no idea what he's going through. For that matter, you and I have no real idea what they are going through, only that they are suffering terribly.
Recognizing that everyone's experience is different and I might be overgeneralizing, there are related phenomena that are worth considering in case they might apply to your situation. Like many other people with CH, my daughter only very rarely wants to talk about CH. She just wants to try to forget that it's real. When an attack is over, she wants to go back as much as she can to "normal" life and not dwell. There are a lot of people who come to this board when they are in cycle and stay as far away from it as they can when they're not in cycle. Also, there are many reports about people with CH doing all they can to hide what they are going through from others. There was a woman here some years ago whose husband and family had never seen her having a CH attack. Maybe that's extreme, but we have had many supporters here over the years feeling bad because the person with CH wanted them to go away, leave them alone, when they were having an attack. I'm going to go ahead and say that I think that's in part because no one wants to be seen being that vulnerable, that helplessly in the control of something so awful. I know there are other reasons, too, but I do think that's one of them. I was reminded a little of that today in a post by @Dana129, who wrote about watching a video of someone having a CH attack, "I felt like my safe haven had been somewhat breached when someone had posted a video of an attack." So I'm just saying that CH is probably unlike almost anything else in the way that it can push away people who want to help. Many people here have worked that out with their supporters in one way or another, but it can be challenging. He is blessed to have you there.