Hi Lunar,
If I understand the readings correctly, your MCV (VGM) does indicate that you may be thal minor. Combined with normal iron levels, it does look like thal minor is probable. However, your hemoglobin and hematocrit are good, so it doesn't look like thal minor is causing any anemia. If these were much lower, you might have to be concerned about absorbing too much iron with the vitamin C use, but when the hemoglobin level is normal, excess iron absorption will not normally take place. I see no reason to be concerned at all about taking vitamin C or any danger of absorbing too much iron.
A hemoglobin electrophoresis test should be able to confirm the thal minor diagnosis. I think the main thing you should think about is if you have any children, they should be aware of the possibility that they are also thalassemia carriers. If they are, they need to be aware their partners should be checked for thal carrier state before having children.