Oh! I forgot the best gelato of the province in Fano at gelateria artigianale Makì in piazza degli Avveduti.

In Urbino try osteria da la stella
in Fermignano I second the suggestion you received: Trattosteria
You should not miss Osteria del cucco in Urbania and a newish place in Cagli called Osteria da Nani serving very good organic local food.
Also in Cagli for lunch, aperitivo or buying some great cheeses, wines and much more go to Alimentare.
Enjoy your stay!

Prugnolo is indeed "sloe" or blackthorn, a blueberry-colour berry that grows on thorny bushes. Widely used in the UK for making sloe-gin. In this area (Urbino, Northern Le Marche) after filtering your prugnolo liqueur (that includes sugar and spices) you cover the berries with good Sangiovese wine and let sit for a couple of months, the result is a beautiful dessert wine that pairs brilliantly with chocolate!
Mind! Prugnolo is also a mashroom.