Your red blood cell count doesn't seem to be extremely elevated, so I'm not sure if it's a real concern (but I'm not a doctor so I could be wrong about that).
MALT Lymphomas (a type of NHL) of the thyroid are often associated with Hashimoto Thyroiditis. MALT Lymphomas frequently arise in tissues that are chronically inflamed in response to either autoimmune disease or chronic infection. The chronic stimulation of lymphocytes may predispose to the development of this form of lymphoma.
So, regarding the separate blood supply to the thyroid: It was once there but is now gone and has moved somewhere else? I have never heard of a blood supply to a tumor moving somewhere else. Is your thyroid enlarged? Have your doctors considered removing the thyroid for biopsy? They may be able to do a needle biopsy, but it is a lot less accurate.
As for the lumps in your breast, I hope you have had them looked at. I can tell you that lymphoma can show up in the breast as well as in the more common areas (underarms, neck, groin, etc.). It's rare, but it does happen. I should know as I was one of the rare ones.