10-month relationship; Too early to have these problems?

My boyfriend (who has been coping with ADHD his whole life) is 36 years old.  We began dating at the beginning of this year.  Soon after we started dating, he mentioned his ADHD and the medication he was taking to help with symptoms.  While I was glad he shared this information with me, it was during our courting phase and there were absolutely no harmful ADHD relationship issues even remotely occurring at that time.

6-months into our relationship, he went from all-in to all-out.  He completely lost interest in me.  And for the past three months, we have been on the verge of letting go.

Just over a week ago, my boyfriend listened to the first chapter of The ADHD Effect on Marriage.  The audio book was given to him by a close friend who's marriage ended because of ADHD symptoms.  After he listened to the first chapter, he let me listen to it.  We were instantly stunned to realize these issues were so very common in ADHD relationships.  We have listened to a few more chapters together, but we are still arguing.

He never knew that his tendency to jump from relationship to relationship was based on his ADHD.  It's eye opening for him to have some answers finally, but I think he's too tired to even try to save OUR relationship.  My biggest fear is that I will have invested so much love and energy and time into learning about this part of him, but he will just want to start fresh with someone else, and use the tools he learns with her.

We've had painful moments between us (an emotional affair on his part) and a few lies.  Knowing his ADHD was not being managed, I have said I want to move forward and not linger on a couple of months that just happened to be really hurtful for me.

Non-ADHD partners and spouses....  How do you reach him to tell him that the whole he has dug IS fully capable of being filled in again?