Your experience sounds very similar to mine. I was only (seriously) diagnosed and treated for the last two years of my six in the program. I completed earlier this year, so hopefully that’s some encouragement to everyone.
As for disability accommodation that’s perplexing that they wouldn’t extend that to a 4-day qual exam. It’s been many months so I’m curious whether your negotiations were successful. I think your approach was correct–you’ll catch more flies with honey than vinegar. But hypothetically, any United States institution unwilling to negotiate on a “reasonable accommodation,” would be at risk of violating the Americans with Disabilities Act, so hiring a lawyer who could deal with the university’s general counsel office would be an unfortunate but viable next step.
Hope it didn’t come to that and hope you passed with flying colors! I actually had 2 weeks for quals and did some of the most focused work of my life (untreated!). The urgency helped me focus, and I developed a writing routine with plenty of breaks resembling a Pomodoro approach. So even if they are intransigent (and you don’t want to get a lawyer or talk to the GC), you can succeed!