Assuming I have my facts straight:

Sicily has silk (40), sugar (40), and grain (30). So the basic yearly income should be 110 * 0.52 = 57 florins. Add in the Merchant's Guild (140%) and you get 80 florins. You should get this amount for local trade, plus this amount for every trade partner province you have linked into your web of ships (allied or neutral province with a port, goods not traded if both provinces have them).

If by some miracle allied or neutral factions have some semblance of a trade network connected to Sicily, you should pull in 20% of what they are getting.

Sicily has a 540 base farming, so the farm income should be 540 * 0.52 = 280 florins, multiplied by whatever farming improvements you have made.

A cathedral will add 52 florins per year.

The acumen of both the Sicilian province governor and the king will affect these numbers, as well as their vices and virtues.