Hi, I guess the easiest way, that not involves any programming would be:
1. If you use front page template, leave those two widgets empty, so you could use three footer widgets.
2. Then use a plugin to manage appearance of widgets only in certain scenarios. You could Use Jetpack with its Widget Visibility, that is also available as separate plugin:
https://wordpress.org/plugins/jetpack-widget-visibility/
Or this plugin is also a good one:
https://wordpress.org/plugins/content-aware-sidebars/
I guess that it also can be used to manage footer widgets.