Earlier quoted context omitted.
That sounds similar to me. I was diagnosed unexpectedly at 38 and it changed my life. There is a good chance your internalised coping mechanisms are adding undue stress to your nervous system, making you tired and depressed, and ironically exacerbating the conditions for symptoms to become more disruptive (when you're tired, aren't eating properly, hyperfocusing too much and wearing yourself out, working late nights…
What's the benefit in knowing for sure?
Mostly the benefit is understanding yourself and allowing a measure of grace for your challenges. It helps you calibrate your goals, and be self aware when making decisions that you may be suffering an executive function deficit, and to seek known good supports for managing impulse control challenges.
There was a time when I started taking stimulant meds, but still felt the need to finish off-topic ideas to completion. It took a lot of learning to understand that my instincts need scrutiny, and that I don't have to beat myself up for not being able to do impossible things on a regular basis.
I like myself better. I get more of the important stuff done. I can even relax from time to time. I also accept that I will always have some unique struggles and special abilities.