Hello again, mooneydiva;
what a wonderful itinerary! I'll believe you if you say you don't like sea days much, and it's a good thing; you've set quite a pace for yourselves-- 13 ports in 15 days.
I have been to most of the ports and my favorites are Gibraltar(most interesting), Cannes(most picturesque) and Florence/Livorno(most historical). One bit of advice: don't try to do Florence AND Pisa from Livorno; you won't see much of either. Take tha all-day excoursion to Florence and save Pisa for another trip.
As for your concern about Casablanca, we had a very interesting excoursion there, part walking tour, part motorcoach, and never were the slightest bit uncomfortable or apprehensive. Our policy is to stick with ship-sponsored shore excoursions our first time anyplace; we feel confident no cruise line is going to put its passengers in harm's way. You didn't say, but I am assuming it is your first trip there. Then, if we feel comfortable with a port, we may strike out on our own.
Barcelona is where you really have to keep your wits about you. We have never had a problem but we've heard of many incidents of pickpocketing and purse-snatching. You just have to follow some really basic safety rules: stay low-key, don't be a flashy dresser, don't flaunt expensive jewelry and watches, mind your belongings and your surroundings.
You should have an absolutely wonderful trip; the Star Princess is a magnificent ship and you've selected a dream itinerary.
Keep in touch.