Is CT cardiac calcium scan accurate in diagnosing mild ectatic ascending aorta? Have fam. History of heart disease (father died at 46 with chf) and slight heart murmur. Should I have other tests done

No. You need an aortic ultrasound to determine if it is too large. A calcium score of the abdominal aorta is useless. A vest x-ray with abdominal view can tell you if you have a mildly ecstatic aorta or not but that is not harmful. If your doc is concerned the best test would be a stress test of your heart. Talk to your doc.
Ectasia. The ectasia is likely. You need good BP control, lipid control, not smoking, cholesterol control in any case and that's all you can do about the ectasia anyway.