Patient has polycythemia vera, as evidenced by erythrocytosis, granulocytosis, and headaches & diziness. EPO is decreased due to erythrocytosis. Decreased LAP would indicate CML, not PV.
"PV is a neoplastic (clonal) blood disorder with autonomous (EPO-independent) erythroid proliferation. Because of the existence of a negative feedback mechanism, the erthrocytosis in PV down-regulates EPO production and results in below normal serum EPO levels. In contrast, an EPO-driven erythrocytosis characterizes secondary erythrocytosis, and this condition may be associated with either high or normal serum EPO levels."
Increased Levels of Myeloid cells ( Erythrocytosis, thrombocythemia, and granulocytosis) plus Dizziness and Headache increase the suspicion for Polycythemia vera.
Low EPO in PV due to Negative feedback on EPO release by kidney.