Can I create a custom assessment form to use online for churches on my website?

You can check these guides to build your first Form.

Guide: https://www.jotform.com/help/2-How-to-Create-Your-First-Web-Form

Guide: https://www.jotform.com/help/46-Quick-Overview-of-Form-Fields

Feel free to check our templates:

https://www.jotform.com/form-templates/

1) Add your questions into native fields such as "Single choice" or "Multiple Choice" fields, and assign a value to each option: https://www.jotform.com/help/301-How-to-Assign-Calculation-Value

2) Next, perform the calculations: https://www.jotform.com/help/259-How-to-Perform-Form-Calculation-Using-a-Widget

Thanks.