Q1. Neptune is about thirty times as far from the sun as is the earth or as the earth is.    How to write?

Q2. 0.5 miles    Does it need “s” ?

Q3. impressive VS impressing           How is it used?  How different?

Q4. The soil is very salty like deserts and is capable of retaining much water.
        Can I omit the second “is” ?

Q5. Community life must clearly be of some advantage to the animals.
                   “of”  means what??   How to use??

Thank you