He says that me “bitching” about the mess is just like if he were to complain about my PTSD/depression/anxiety. That the mess is because of his ADHD. Is this true? Do those of you who have ADHD leave stuff everywhere and expect your spouse or whoever you live with to just accept it or clean it for you?
I have ADHD-PI and treatment-resistant major depressive disorder. Your husband's tendencies remind me of some of my own issues, although his stances on them seem immature to me. That's to be expected: I got diagnosed as a child and have been working on this for fully two decades.
First, I have a comment about what appear to be conflict-fueling behaviors, and I say this after two decades of Adderall XR being my wheelchair: amphetamine puts you in a stressed-out state. One of its actions is to activate the fight-or-flight response, and in my opinion, the historical record is littered with examples where dopaminergic stimulants - a group that includes Adderall XR - skews fight-or-flight toward fight.
With amphetamine, you are superhuman. Endurance, persistence, and fixation are expanded to a degree that is incomparable to even other stimulants like caffeine. These are useful tools when trying to study. They can be counterproductive in the domain of interpersonal relationships, and must therein be managed carefully.
As for your second question, it is the case that ADHD makes it more difficult to maintain a clean and tidy space. Imagine that your mind was automatically thinking of so many things that you were too tired to keep your mind on any task no matter how important. It can make it difficult to care even for oneself. However, it is absolutely unreasonable for a 38-year-old grown man to feel so entitled to the fruits of the labor of others to expect anyone but himself to clean up his own messes.
How both of you interpret and tolerate the cleanliness of a space, and feel compelled to clean it, is unlikely to perfectly correspond. If you're asking for advice, I'd recommend compromise around this matter.
Remember: ADHD is a curse. It is a nightmare from which you cannot ever fully awaken.