How serious is having microvascular angina?

Serious. This is small vessel disease. It is usually best treated with Ranexa (ranolazine) - but since each patient is different, and may have other comorbidities, a comprehensive evaluation by a cardiologist is essential.
Depends. It can be very serious, since it cannot be treated by stenting or bypasses. Drug treatments or transplantation are possible treatments. Some patients find benefit from external counterpulsation. Diabetes often causes disease in the smaller coronary arteries.