This is a patient forum so we offer support and information based on our own experience, not medical advice.
That being said, i would guess your father has stage 4, as grades only go up to 3. In stage 4, his cancer is advanced and has spread outside the brain to other organs.
I am so sorry to hear about your father, but there is not enough detail to comment/guess about his prognosis, and what you have given sounds sadly not positive. I would focus on keeping him pain free and rallying the family together.