2" diameter at 2000 rpm is more than 1000sfm and 8ipm gives a chipload of 0.0013 per insert in the cutter.
I think your speed is way high and your feed way low.
Did you change the inserts before slowing the speed down? I think you probably rubbed the edge off them with such a high speed and small feed.
You are limited in power so probably you cannot do several hundred sfm with a decent chipload such as 0.01 per tooth so I think you will have to poke along as you are maybe at an even slower feed. It probably is going to make a lot of noise because you are machining tough stuff.