Information that populates SC form I-335 comes both from the return itself as well as from the "Tax on Active Trade or Business Income" dialogue in the South Carolina interview.
Enter the South Carolina interview, and proceed until your find the screen with the title "Tax on Active Trade or Business Income". Answer "yes" to the question "Do you want to use the optional income tax rate to compute the tax on your active trade or business income?". Then answer the questions on the following several screens to complete the I-335
To answer your second question, please see the following FAQ. Note that you may to upgrade from TurboTax Deluxe to enter this deduction. In TurboTax
Desktop Home & Business, the navigation is to "Business
Expenses->Other Common Business Expenses->Insurance Payments"
- https://ttlc.intuit.com/replies/5802930
