Your feedrate seems reasonable, I am surprised that your max is 200 IPM.
I usually train shops on metal cutting machines, but I remember a job teaching in Albany, GA to make bus floorboards, 3/4 inch thick and we were feeding around 300 IPM.
I also remember we used a 1 flute cutter that could drill holes and also mill all contours.
Good luck, Heinz, see mill program examples on doccnc.com