Does the web form have "save function" for the customer in-case the form is long?

It is possible to save the form and continue later. You can enable the Continue Forms Later feature inside of the Form Settings.

I have enabled the setting noted above, but there is still not a "save" button on my form. I'd like a button that people can click to Save and then access the link via email to pick up where they left off later. How can I best accomplish this?

I have checked your form and noticed you don't have the Continue Forms Later function enabled on your form.

To enable Save and Continue Later on your Form, follow these steps. SETTINGS> FORM SETTINGS SHOW MORE OPTIONS> Continue Form Later and select enabled. 
Let us know if you have more questions.