how can I set our business logo as the default home screen icon when saving this form to my iphone home screen?

You can use the Add To Home Screen Widget to set your business logo as the home screen button logo.

http://widgets.jotform.com/widget/add_to_home_screen

To add the widget to your form, simply follow this guide: How to Add a Widget to your Form. Then to add the logo, simply insert the URL to the Logo Image URL field from the widget wizard.

Please note that the image should be at least 180px * 180px.

If you need further assistance, do let us know.
Regards.