yeah the 30% coconut is going to be highly cleansing, without a high SF. Good thing is, save some of those bars to compare with other recipe's you make in the future. You'll get a great comparison.
No idea on the soap ring. I'm usually taking showers and don't notice it though.
Yeah the itch could very well be the cleansing of all the oils in your skin, from a high cleansing soap.
With the exception of salt bars, I never go over 15% on Coconut. Lots of people seem to have no problems up to 20%