Myelofibrosis is a genetic disease that stops your body's production of healthy blood cells. The result is severe anemia, which causes weakness and fatigue.
With a platelet count of
11,000, the main concern would be his bleeding risk. Platelets are responsible for helping our blood to clot. Since his platelet count is really low, he could start to bleed at any time and not be able to stop. If you notice bleeding from his gums, nose, penis, or rectum, I would call his health care provider right away. As a precaution, make sure his environment is as safe as possible. He should not be shaving with a blade (use an electric razor instead), as if he gets cut, he may start bleeding and take a long time to stop. Minimize clutter in his living areas, so he will not hit himself on anything in the way.
I should also mention that his hemoglobin is also extemely low, which will cause him to fatigue easily and become short of breath with minimal movement. Since the blood transfusions are not helping your father anymore, there are drug therapies they can try. These include hormones, like androgens and/or steroids, hydroxyurea, and thalidomide. Hopefully, they can try these medications on your father with some success. I wish you and your father luck.