Nope, you played your opening wrong. You need to recognize the threat of Milan to you. Take out Milan ASAP and declare war first. Papal excomm isn't a life saver. Just pay off the pope to let you kill Milan in peace. If you look strong, Sicily will simply have their big stack near the border to Bologna hesitating to attack. Then simply amphibiously land two halfstacks near Naples and Palermo simultaneously to take them. Their big stack can't relieve their cities in time. Palermo is often a citadel early on which can let you pump out Venetian archers (awesome units).

You should also not be beaten to Zagreb by the HRE. You have an army in range of it on first turn.

Your forces in Crete can land right next to Corinth on the first turn and siege it on the second. Key is to attack instead of waiting to be attacked.