I am 41kg and suffering from severe food allergy anxiety, although no clear allergies beyond kiwi, watermelon and sulpha-meds. my mind is my enemy. what are the odds to really have an anaphylaxis at 40+ out of the blue to justify this fear of eating?

You are perfectly right that your mind is struggling with food related anxiety. The odds are very low of getting an anaphylaxis type of reaction, you definitely need help and a psychologist specializing in eating disorders should be part of your team. Physical exercise has the potential of helping by creating healthy hunger and alleviating anxiety.