Parenting with an ADHD partner

My husband is a great dad, really.  We have four teenagers.  He loves his kids, spends tons of time with them, is super involved, etc, and he has always been like this.  His biggest parenting flaw is that his ADHD tends to make him have disproportionate knee-jerk reactions.  If the kids do something wrong, or I have to relate a problem, he tends to over-react, frequently without knowing all the details, and dole out some ridiculous consequence that he'll completely forget about two days later and won't follow through with.  This is a difficult co-parenting situation.  I want him to back me up when I encounter a problem, but I want him to actually understand what's going on so we're on the same page.  He sometimes decides on a punishment and two days later when I'm trying to enforce the consequence, I learn that he's let it go.  Or he might over-react and I'll take him aside afterwards and try to explain the details and he'll get mad at ME... even if he recognizes he was clearly in the wrong.  The kids don't like approaching him with their grievances, which hurts his feelings, but they have experienced his reactions so they come to me to present to him.  And then he lashes out at me because he wants them to come to him directly.  It makes both the kids and I hesitant to discuss these kinds of things with him.  I HAVE to, as a parent, but I hate it because it may not be a reasonable "conversation".  We've discussed making sure we're on the same page before determining appropriate consequences many times, and we usually are until he impulsively goes rogue and then it's a total mess.  The kids get confused, I get frustrated, and he can't understand how any of it has anything to do with his reactions or behavior.

Does anyone have any experience with kind if thing?  Were you able to resolve it?  If so, what did you do?