Laughs in ADHD with you, so hard she's crying

Agreed. I forget everything. My best friend has been my best friend for 25 years and only 5 years ago did I start getting her birthday right. (2 days before or 1 day after, it wouldn't stick, and like and idiot I'd have to call her for her family's birth dates every year because I didn't transcribe it over before I tossed the old calendar. I know them all now though, I was always off by a couple days).

That's probably my biggest fail so far and I love her to bits. Adore her to pieces but her birth date seemed "wrong" in my head. It was the proverbial rereading the paragraph a million times, yet I can remember when the Titanic sank off the top of my head and my highschool locker combination.

It's possible he's an absolute tool, but maybe he's not NT and doesn't know it.

This is why:

He forgets often and doesn't like to be told what to do.

The thing about ADHD is we absolutely LOATHE being told what to do. We are not really the boot camp with the screaming sargent type. We'd probably flip him off and do the opposite because we all got some ODD. That's totally cool, its who we are and we're build a little different and really, most people don't like to be told what to do.

The flip side is, we kinda need a schedule, need guidance because we may get stuck/lost/need help but won't ask.

It really sucks, but if he's genuinely upset, it may be because he really did have the best intentions and he got in his own way again. Its kinda our thing. Does he say he'll do better but doesn't? Does he beat himself up over it? Can he fixate on things for a long time? Does he forget to eat or binge eat when he's bored/stressed? Is he clumsy? Does he lose things? Is he late a lot?

You're a million% NTA, OP. Not even close, but maybe he should get evaluated...just in case.