JAK2 Mutation - Effects and Questions

Have JAK2 mutation verified twice; one year apart and from different labs. As I understand, it may cause polycythemia vera, essential thrombocytosis, or leukemia. My hematologist has not provided any real info on this mutation so I've been researching via internet. I knew leukemia is cancer but was disappointed to find out today that the other 2 are blood cancers as well. I have been seeing a hematologist every 3 mos. about this since my 2nd blood clotting event in 09/2016. To date, all my blood factors have been in the normal range. Here are some of my questions: 1. Is it typical to verify this mutation well before it triggers one of these diseases? 2. I know early detection of cancer can be a real plus, but is there any research or experience that supports proactive steps that can be taken to deter the onset of any of these possibilities? 3. With polycythemia vera and essential thrombocytosis, is blood letting the primary treatment? If so, can the blood be donated? 4. Since none of my blood factors have ever been out of the normal range to date, no specific result of the JAK2 mutation has raised its ugly head. Is this normal? I'm not typically a worrier. In fact, I do really well with things like this once I know what I am dealing with. Information becomes my sword which allows me to take worry and nip it in the bud.