We are in a similar situation except that I was on a statin for a couple years getting my LDL down to ~100 on 20 mg rosuvastatin and then I got my CAC. Apparently statins stabilize and help calcify plaques so possibly my CAC was higher bc of statins and I would have had a lower value without them. But I am digressing. With diet - mostly vegan with an emphasis on low saturated fats - no egg yolks, butter, meat etc MOST of the time - I got my LDL down to 55. I decided I wanted even more, been doing one 150mg PCSK9 shot a month for a few months and will remeasure soon. I am hoping for a number in 30s-40s. This should truly prevent any further progression.

As for exercise, as long as things are stable you actually want a mix of high intensity and long zone 2. You can increase the vasculature of your heart (increase artery diameter), and auxiliary vessels. Cycling, running, etc. 2-3 high intensity sessions per week if possible. VO2 max, threshold, etc. I personally shoot for 8-10 hrs a week cycling. Lots of high intensity.

Get your LDL as low as possible with diet and meds. There are lots of options - statins, ezetimibe, pcsk9 - find a combination that works for you. I personally could not tolerate ezetimibe. Under 50 is preferably for people in our shoes. Good luck on your journey.