If you are having a lot of blood removed, you are loosing iron. Then the implications if dietary iron may be different. What changes do you see to ferritin?
Low B-12 can be from low stomach acid or use of heart burn medications and then there can be risks of poor mineral absorption and mineral deficiencies which can in turn lead to other health problems. See magnesium below.
Do you track your blood pressure at home? That might be indicative of when you need phlebotomy. If high hematocrit reduces or contributes to low blood flow in the kidneys, increased erythropoietin (EPO) production may result. So the condition could be self amplifying in some cases. Any condition that reduces blood oxygenation or blood flow is a contributor.
You can use mini aspirin to improve blood flow. Do not expect major effects, may help keep things from getting worse. Fish oil is also a blood thinner. Arterial muscle tone is important and a magnesium deficiency would make that worse. Most are magnesium deficient. If legs or feet can cramp or you are able to deliberately make a muscle lock up, you are deficient.
Dehydration is a problem as it can cause periodically reduced blood flow that might cause the kidneys to produce more EPO.
While TRT is associated with this problem and may be the trigger, there are other factors.
Elevated blood pressure may be a cause in itself as micro-circulation in the kidneys could be affected. This ties into many aspects of aging and health.