So if there is a solution that is somewhat effective at medicating a disability it isn't a disability ?

Stimulants are effective but they don't make ADHD disappear

Medication is a privilege that many with ADHD can't access. It also doesn't work for everyone. Are those people not disabled?

Also, ADHD is more than struggling to focus, or to sit still. Many of us struggle to start tasks, manage money, keep things tidy, or manage time. These issues can cause so many problems in life, ranging from inability to hold a job to relationship issues. Once the medication wears off, these symptoms rise back to the surface; because ADHD medication isn't a cure, it's symptom management.

A disability doesn't improve with medicine.

I think I understand what you're saying, but disabilities can absolutely improve with meds. Not all of them, and not all the time, but it sounds like that's what your ex-wife's experience was. She had disabling conditions, but it was more manageable when she took her meds. Despite this, there are aspects of her disability which were (are?) still challenging.

To me, THAT'S the experience which defines disability: you've got a condition which, despite yours and your doctor's best efforts, continues to express itself. And even then, I can see a lot of potential issues using that definition in terms of government support. It's compicated.

If your ex-wife found herself in a situation where she had to go without her meds she'd certainly struggle a lot harder than with her meds. How is that any less a disability than a PTSD victim needing antidepressants to quell their unending anxieties, or someone hard of hearing needing electronic hearing aids in order to hear better?

ADHD is objectively a disability. Medicine to make it easier to deal with doesn't make the disability stop existing. Hell, there's a number of people for whom stimulants don't work, or who need unreasonably high doses in order for it to work. The existence of medicine doesn't make their disability less disabling.

This is a pretty deep question, and there's a lot of debate about it. I'm still on the fence, myself.

Goodness, there's a lot of hardcore denial in your edit. I suffer from a similar level of "society/people expect utter perfection of myself" so I understand why your instinct is to deny the possibility of having a disability.