What do you do if scheduling and organization don't work for you?

Hi, I'm the spouse of a person with ADD (no HD).  We know that scheduling and a routine could really help dissolve so many of our ongoing conflicts, hurts, and resentments.  Unfortunately, we've discovered that my husband, who has ADD, cannot stick to any one routine or organization system consistently.  He's very creative and likes to invent his own methods.  That's fine, however, he will continually reinvent new ways each and every time.  For example, around balancing the checkbook.  He doesn't have the patience to learn or be taught the recommended way of doing it so he invented his own way.  It worked (although it was highly risky in my opinion).  But he cannot be consistent with the method he initially worked out, he had to change that every so often so I could never have learned it if I wanted to.  I've theorized that he can't remember how he did it before so he invents a new way, but also he admits he does not like to stick to any one routine.  So if having a consistent schedule and planning is key to successfully managing ADHD - how do we make this work for someone so adverse to consistency?  We've tried so many times - scheduled days and times to meet to discuss our upcoming work weeks and weekends.  He uses a day planner.  Much to my distress, he can't consistently keep scheduled meetings with me and he cannot consistently stick to anything planned or agreed upon.  We are on the brink of divorce regularly  and I'm at  a total loss as to what to do.  We know what could work and he agrees, but he just can't do it.  He doesn't have the time for coaching or therapy (we've done that).  Anyone have a similar experience and have resolved it successfully? Thanks!