All of this advice seems really good. The only one I am reluctant to follow is getting a CT or CTA scan.

For reference, radiation levels:

Chest X-ray: ~0.1 mSv (millisieverts)

Head CT: ~2 mSv

Chest CT: ~7 mSv

Abdomen–pelvis CT: ~10 mSv

CTA (angiography): often 10–20 mSv

Are there non X-ray diagnostic imaging scans that can detect arterial plaque?