This is a subject that interests me, as a practitioner.
My recommendation would be to find a physician to administer 30,000mg of i.v. ascorbate three times a week. Find a cardiologist/vascular surgeon who is willing to work with you and do weekly or monthly ultrasounds, to observe any change in the aorta. My prediction is that over time the aorta will return to normal dimensions.
The outer layer of the aorta is called the adventitia. It is composed mostly of collagen which is highly flexible. Loss of collagen over the years results in the dilated (loss of elasticity) aorta. Your body cannot make new collagen without vitamin C. Your condition is serious which requires a more aggressive approach. Oral vitamin C will probably not do the job rapidly enough.
My reasoning is that a chronic vitamin C deficiency results in a fatal disease called scurvy. If I recall from medical school, the victims died after their aortas dilated then ruptured. It would not surprise me if your condition corrected in less than a month with aggressive treatment. The result should last the rest of your life if you continue to supplement with vitamin C.