Contact the material suppliers for the particular material type you are using. They should have wear and tool material recommnedations for the plastic.
You must be careful when designing a full fillet radius. Some people define a full fillet radius as a constant radius arc connecting the two involutes. Others define a full fillet radius as a constant radius tip on the basic rack that generates the tooth form or on the tip of the hob tooth...
Your ring gear pitch diameter divided by the sun gear pitch diameter plus one is your planetary ratio, approximately. Given your dimensions, you cannot get there from here.
