Sydness - thanks for posting! Your ds sounds similar to my ds10. He's been tested in the 98-99.9% too, but has visual deficits (convergence insufficiency and others), has dyspraxia, SPD, issues with handwriting (possibly dysgraphia), etc. - which has presented a conundrum. He was misdiagnosed with PDD and ADHD.
Ds, too, read early, but initially through sight and whole language. He struggled with phonics until I got him to memorize it with humorous cartoons. He might have stealth dyslexia but if so it has flown under the radar on various tests (same could be said for the dysgraphia and possibly dyscalculia as well). Some of your dh's issues may be related to dyscalculia too.
Interesting about handedness because my ds was completely lopsided, abnormally early right handed abnormally due to some physical conditions from birth, which also affected his neurological wiring. Similar to others, though, dh is right handed but kicks with his left foot. My sister is a leftie. Ds10, Dh, and my sister were all breech babies, though dh flipped in the last 24 hrs. I don't doubt there's a similar situation in terms of neurological wiring with preemies or other babies.
I often think the development in utero can greatly affect the neurological wiring, particularly with my ds and sister, that cannot be fundamentally changed so to speak. It becomes more a management issue and a matter of ways to compensate. OT, vision therapy, neurofeedback, and other therapies can help a lot; my son has had all of them for years on end.
At this point, I'd suggest having a behavioral/developmental optometrist assess your dh if you haven't done so already and possibly an OT. Both could help your dh manage and function more smoothly and make life more manageable and less frustrating. I think you may see more results with vision therapy if it's warranted; the one drawback would be that it's often expensive and not covered by insurance. But even with vision therapy or neurofeedback, there's a limit to what can be accomplished and you'd have to set parameters on expectations, goals, and objectives.
From a long lens perspective, I'd say look at various famous 2e people (celebrities, etc. - admittedly a lot of them will probably men though) to see how they've succeeded despite their limitations or special needs to alleviate anxieties. Google - famous people with dyspraxia or famous people with dyslexia. You'll find everyone from Daniel Ratcliffe (ie. Harry Potter) to Henry Winkler.
Take heart. While there are definitely disadvantages to dyspraxia, dyslexia, dyscalculia, etc. (and I do have empathy and sympathy as a 2e parent!), there is a flip side as well to these diagnoses and conditions. Some believe that it helps to enhance creativity and would not still be in the proverbial gene pool if there was not some evolutionary advantage to having them. I think the trick with being a parent here is to concentrate on the strengths and to diminish or find ways around the deficits and weaknesses, which isn't always easy or fun.