Hi DePaw,
My wife's sister has Auditory Processing Disorder rather severely, and it sounds like your description of symptoms.
My wife has been Dx'd with Asperger's and Social Anxiety, but she definitely has some APD-ish symptoms. She prefers subtitles turned on. She has trouble hearing the meaning of what people say (but for her, as opposed to her sister, this sometimes means that her brain fills in the blanks with some pretty bizarre stuff.)
In both of their cases, symptoms seem to be directly proportional to fatigue, hunger, and low energy levels. Stress makes it worse, but we noticed that *chronic* or extended periods of stress are what make things harder, not brief or acute stress. Nutritional status, especially blood sugar seems to be key.
I am not a research expert on par with other members here, but I/we have a (poorly supported, layperson) theory that some of these LD's, autism, maybe some forms of ADHD, might really be forms of localized insulin/glucose resistance or "pre-diabetes." (Epigenetic downregulation of aromatase, RORa, or insulin receptors or other glucose metabolic factors that would lead to insulin resistance? ) Our son is autistic, and his symptoms also track with "tiredness" and (we think) blood sugar. We have lots of diabetes in previous generations in our families, and we are all sensitive to food, sugar levels etc. in the manner of "hypoglycemics" or "pre-diabetics," however none of us are formally or systemically diabetic.
Based on these observations (however unscientific) we have been experimenting with solutions as if we all have diabetes, (or brain-region-specific insulin resistance.) It's been a really interesting journey, but it's hard to rule out placebo effects and the positive effects of just plain getting healthier.
Anyhow, we have noticed results from the following interventions, some of which might be useful for you to experiment with:
-Eating like a hypoglycemic: Whey protein shakes in the morning, 100% avoidance of High Fructose Corn Syrup, fiber, probiotics, plus other adjustments that help diabetics (the first two *seem* most important.) Over the past 4-5 months this has been massively helpful for their moods and the APD symptoms.
-Regular exercise (of course.)
-Magnesium Taurate - Not sure exactly why, but this has been useful. Makes me sleepy, but my wife gets energy and a big boost to mood from regular use.
-Sulbutiamine / Thiamine: There are lots of posts here on Sulbutiamine (an unregulated drug/supplement that is apparently a fat-soluble form of Thiamine.) These were interesting because diabetics' insulin resistant cells apparently take up less thiamine in proportion to the taking up of less glucose. High dose thiamine is beneficial to many diabetics, so we tried Sulbutiamine thinking that, as brain-targeted Thiamine, it might be useful. Turns out my wife and sister-in-law are *HUGE* responders to sulbutiamine... It has been almost magical with regards to the APD symptoms. Unfortunately, "tolerance" (or, I suspect, depletion of glucose stores) sets in pretty fast (<1 week at 300mg/day.) So we are experimenting with dosage/cycling schedules and high doses of old-fashioned Thiamine. This is very exciting, but not at all dialed in yet.
-Genistein Soy: Estrogenic, but might help with insulin resistance. Wife started adding to her protein. This has been <2 weeks, but it seems to be helping the Sulbutiamine and Thiamine to work more strongly again (???)
Other thing we are going to add, one-at-a-time:
-Chromium supplements
-Cinnamon
-Possibly Berberine.
Anyhow, I wish I had more hard data for you, but I hope that gives you some ideas to explore.