Inconsiderate, thoughtless, clueless or just ADHD?

I have been seeing my ADHD diagnosed boyfriend for a little over a year, we are both 39. There have been many ups and downs but I believe he tries hard to be a good "significant other" despite the ADHD. Yet there are continuous issues that keep popping up that I am trying hard to not take personally and put into perspective (accounting for the effects of ADHD) but I am having increasing trouble doing this. (He has a prescription for Ritalin but often forgets to take it so the benefits are questionable).
Since we are both divorced, have busy/challenging careers and children from our first marriages, our time together is limited. So because of these reasons I have tried many times to put a schedule in place so that we can set aside time to see each other. This has been a very frustrating experience. Although he has made progress over time, most weeks will come when I don't know for sure if I will be seeing him and usually have to wait until a few hours before our normal date night for "confirmation" that I will actually be seeing him. And when I do see him it's often not until 10-11pm at night because he is tied up with work (he is a lawyer with his own practice so it's not a typical 9-5 job). I have tried to be patient with this schedule and he also admits that it is not ideal but always says "I just have to get through this month and things will be different" or "this is not usually how crazy my life is, this is just a chaotic time" or "once I have enough saved up I can hire someone to help me". But after dating for a year, the patterns are the same, so I'm beginning to doubt that this lifestyle is going to really get better?
The latest conflict comes from his choices for New Years Eve. We both have the night free but he is choosing to attend an annual party of a friend of his rather than spending the night with me. He is trying to free up, Thursday, the night before so that we can be together, but I am hurt that presented with the choice to spend the evening together, he is passing on the opportunity. I really can't imagine spending the night with anyone else than him. Attending the party together is not an option since he is not comfortable introducing me to his friends until I am officially "divorced" which is only a few months away. The divorce has been ongoing for 18 months unfortunately. And was not initiated because of my relationship with him.
I plan on talking with him about how this situation on New Year's effects me (he already knows that I am somewhat upset with his choice) but I don't believe he realizes how much.
In addition, his communication skills are not great. He doesn't enjoy talking on the phone so keeping in touch is mainly via text messaging and not very elaborate.
When I am actually "in front" of him, he is kind, passionate and very attentive. But getting "in front" of him is the challenging part. Also, the lack of planning and chaoticness of his life is driving me a bit batty! I try to approaching issues with a "team like" attitude rather than accusatory, but I'm still feeling emotionally exhausted most of the time.
Is this chaotic, inconsiderate, lack of planning and poor communication behavior ADHD? Or is he just self centered and not invested in this relationship as much as I? I have told him that I feel very strongly for him and believe that I am falling in love with him. He has told me he feels the same way, and he has never had such a strong relationship with anyone else before (aside from the happy times of his first, short lived, first marriage).
What really is the prognosis? Is there a better way to handle the situation? Or should I walk away like people close to me have suggested since he doesn't seem to be capable of ever really making choices that are more in tune with what I view as "normal"? I have read many articles on the topic of ADHD and relationships and it has helped me to understand him better, but I'm still left feeling like the situation is not ideal and I'm always left wanting more of him.
Thank you for reading this long description of my situation and for any information you can provide!