it looks pretty much OK I think, as long as the rules play well together. I actually would have set up it in a different way, but since I am not sure what you are setting up it might be fine.
Generally there is not much different whether you are running an Explicit proxy or ICAP serverin regards to rules, so there is no need to create a special "ICAP" rule. I would create a blank "top level" rule set which has "Connection.Protocol = ICAP" and import the default rule sets from the rule set library below this top level rule set.
The request you made looks OK. You should be able to test it :-)
Thank you, I'll post comments when tests will be made.