Assuming a 27-29 inch draw length I would suggest a size 300 Carbon Express in which case a 100 grain point weight would yield a relatively good FOC balance and appropriate spine for your setup. If you bump up the draw weight to 65 lbs and your draw length is 29 inches or longer then I would probably start to consider a size 400 instead.

As for the diameter of the field point, I have found that a 9/32 size 100 grain tip to be just about perfect for most of the ICS style carbons on the market...including the CX arrows. The diameter of the tip is just a hair smaller than the insert/shaft diameter.