Once you have been diagnosed with a high calcium score I think there is little merit in further scans (you already know you are at high risk) and you add another risk since you are exposing yourself to additional radiation.
You should take steps to modify your lifestyle but be aware that while you can reduce the risk a little you are always going to be at high risk. Most major studies put the risk of having a major cardio event or stroke at 20–25% within a year with a CAC over 1000 (and asymptomatic!), and a likelihood that an event is probable in 3-5 years.
In addition to lifestyle modifications I think that cognitive behavior treatment can be helpful to help you understand and cope with the stress that such a diagnosis can cause.