Property Taxes?

I am determining the costs of  property ownership in Italy and am confused about property taxes (IMU). This is a two part question using a small attached beach cottage in Trapani, Sicily as an example. (I have dual Italian-American citizenship and will reside in the USA.)

Question 1A: According to the commune's rate schedule, the rate is 10.6% for a property that is not my principal home ("Aliquota per tutti gli altri fabbricati"). But online sources quote a much lower rate (0.4- 0.76%). How can I determine the correct rate?

Question 1B: I don't know this property's cadestral value. I need this because the tax rate is applied to it rather than the asking price. Is there a rule of thumb that can help me estimate the cadestral value? Is this information made public?

Thanks in advance for your consideration. I hope to be more helpful myself in this forum some day.

The cadastral value is public and can easily be seen on a visura for the property.  Ask the agent for a copy.  Alternatively you can get  them easily from a disbrigapratica.   There is no rule of thumb for knowing it however.    If the house remains as it was in the 1950s then it will be very low.   The 10.6 becomes 1.06 when applied to the property, so if you use an online calculator it does this for you...   0.76 is now unheard of....  its almost always over 1.