It sounds like you've tried a lot to control your scalp odor. I am not sure what a diagnosis of "scalp odor" will do. It might help, but it may lead to more dead ends, since "odor" can come for any reason. TMAU causes a fish odor, a maple syrup odor could be diabetes, fecal odor could be candida, etc.
I have had bouts with scalp odor in the past. Your scalp is skin, and just like all places where skin, oil, sweat, bacteria and fungus can inhabit - it can produce fairly noticeable odors.
If I were you, I'd only use pH balanced shampoos and conditioners. For myself, I found Apple Cider or White Vinegar rinses to be helpful. Tea tree oil is good too, so I'm glad you have it in your regimen. There are other antifungals, too. All natural essential oils such as rosemary. Clay such as Bentonite can be great at detoxing your hair and scalp.
If you want to focus on diet, I'd also limit the protein in your diet. Almond milk and beans can be high in them, as can dairy.
Staying "regular" is important, too. I wouldn't change your diet too often, you should give your body time to adjust. I know a lot of people talk about being cured with one or two pills, but for most of us, we probably have some sort of imbalance. Yours could even be hormonal. It takes time to get that stuff in check. Whatever you do, always make sure you have regular bowels. So, probiotics and/or lots of fiber should be part of your regimen.