The furtherest I have ever killed a deer at was 53 yards. At the time I was using a slider which had a sight tape on it, the conditions were perfect, the only reason this was even considered.
Now I shoot a 5 pin sight on my hunting bow. The pins are set at 20, 30, 35, 40, and 45. I shoot a 417 grain arrow at 302 fps and find that after 30 yards the drop is enough that I want pin for every 5 yards after that.
In your case, shooting the lower weight and heavy arrow (500 grains), I would assume your speed is considerably lower than what I am shooting and would suggest 20, 30, and 35 for your 3 pin sight. Shoot two arrows at 30 yards and then shoot two arrows and 40 yards and see for yourself the amount of hold over you would need and then decide for yourself.