I clearly understand what you are going through, the feeling of shame because of your response, a sense of failure, and frustration. I prayed a lot for forgiveness and for self control. My dear wife of 47× years is extremely forgetful.
What I've learned is that it is the disease that causes her behavior and not the person. She's frustrated with herself as well. Fortunately, for her, she does not remember her behavior nor her frustration. Of course, that,'s no help to me.
What helped me to adjust to the forgetfulness is to think of her as a four year old person. What would you expect of a four year old girl and how would you respond to her behavior. This has helped me immensely to reduce my frequency of frustration and level of stress. A four year old cannot rationalize or fully understand as yet, so I avoid doing so with my wife.
My wide is in a four-year-old world of thinking and behaving. I try to learn about her world through observation and experience. I focus on giving her love and affection and learn to work with and around her forgetfulness. Giving her explanations, corrections and instructions do not work.
Be kind, forgiving and patient with yourself. You will make mistakes and will feel frustration. You have a new world, the world that your husband is living in to fault of his own or yours.
Peace be with you, Teri.