Have you ever tried any of the items I have mentioned? Rescue Remedy is the simplest one. Three to five drops in drinking water. And because it is a homeopathic remedy, the amount in the water is very small. Yet it works as far as I can tell.
Also, since cats are quite sensitive to human anxiety, this video, which I have played for myself at night, has helped me and by extension my three cats.
Also, this music was composed especially for cats.
I hve have had my house broken into twice in the past five years, with the most recent break-in occurring in the summer of 2020. That frightened my cats immensely, and it took them three years NOT to be frightened by knocking on the door and unfamiliar people coming into the house. But they are much more relaxed because I have been working on creating more positive energy within myself.