Hi Rowan, wanted to comment here as I can relate to the anxiety you are feeling. Almost a year and a half ago I had a CAC test done and it came back 1168. Needless to say, I was freaked out. Had no symptoms. I see a lot of posts that people eat well, exercise regularly and all the right things and are shocked by their scores. I know there are genetic factors but the more I've learned about food, the reality is I really didn't eat that great, even though I thought I was.
Your next steps should be with a cardiologist to determine if you have blockage. I was extremely lucky that my PET Scan showed no blocked and normal profusion. It was the best news I could have received. I viewed it as a second chance.
You caught your issue before an event so you also have a second chance. I met with a dietician and completely altered my diet. The key thing is I don't feel like I've sacrificed food. There are lots of delicious things that are good for you. And to be honest, the thought now of eating a donut has zero appeal. I'd rather be here on earth longer than the second of pleasure from a donut.
Wishing you the best. Learn about how food affects your condition and make the changes. The mental motivation can be strong if you let it and don't let yourself feel like you have no hope. Because you do.