Long term difficult marriage

My husband was diagnosed with ADHD three years ago at the age of 66. We have been married for 45 difficult years. The diagnosis was a shock and a relief. At least it gave us some answers. He does well on Adderall, but, he will often forget to take it or choose not to take it due to something he may have read on the internet. He has cut himself off from his therapist for refusing to take anti anxiety meds, which he aslo desparately needs. Needless to say, he cannot do anything really. The Adderall keeps him calm and rational, but, he still can't function, such as pay a bill or find a repairman. I have my own health issues and I am grieving over the fact that my grandchildren moved over 2,000 miles away. My husband is unable to empathize or sympathize with what I am going through. Today, I really needed his help with something and he let me down. I sold my SUV since it is too expensive for me to keep and it was the last connection that I had to my grandchildren as I used to drive them around in it. I drove the vehicle to the car dealer and my husband was suppose to be following me to the dealer and driving me home after the transaction. He never showed up! He got lost. He spent 45 minutes driving around in circles within 4 miles of where he was suppose to be. He kept me on the phone the entire time sending me pictures of where he was and asking me to tell him how to get to where I was! This is the 4th time he did that this year. I finally told him to pull over, stay put and I had the dealer drive me to him. Sadly, he was right around the corner. He lost the ability to be able to use his gps. It was on walking mode and he didn't know how to fix it. He gets very upset when these things happen and of course, it was all my fault. The screaming and yelling in my face started. I drove us both home and he continued to get worse. I asked him if he forgot to take his meds and he said that they can cause long term cognative issues and so he didn't take them!!! I was beyond livid! I started hyperventilating and was crushed. Of all days for him to do this to me! He took the meds later in the day and within an hour he was fine, but, he has no idea what he has done to me. Thinks it was no big deal. I am at my witts end. Where do I go for help? How do I handle this? Sadly, I had to tell both of our sons what transpired today. Any advice would be helpful.