Unfortunately when it comes to pages imported from IDX plugins there is little control over the content from our theme.
The only idea I have is to modify the IDX PAGE template we provide with the theme and insert in there the contact form. I don’t know how you can insert gravity form in php (you need to consult the plugin help).
If that helps, then at the end or beginning of that page (where you place it) you can have this plugin contact form.
You will probably need to set in the IDX Plugin settings that the IDX PAGE TEMPLATE is default for the pages you wish to control.
It’s the only idea I have since all this is third party.