Ubermenu is manually integrated throw header builder. Each menu block in header builder has an option “Use Ubermenu” , which you can check to activate the ubermenu for a specific menu.
I checked this option in your current header for the main menu and unchecked the menu’s location integration options in ubermenu settings.
About using a different menu for a specific page, you can create a new header and use it in that page.
In the page settings, below the publish button box on the right, there’s a box with title “(Circleflip) Header Builder”.
You’ll find a select with a list of all your created headers where you can keep the default global header or change it.
If you can’t find that box, go to screen options on the top right corner and click it, then check “(Circleflip) Header Builder”.