Okay, I think I get it now. You want to display the vendors as results, filter them by the food categories and their location.
The main issue with this is, that the vendors are not custom post types, but taxonomies. Taxonomies can not be filtered – taxonomy terms are used as filter criteria. The plugin can show the vendors as results, but there is no way to add filters to them, as the vendors themselves are taxonomy terms. I don’t know if there is any plugin out there capable of filtering taxonomy terms by other taxonomy terms or term meta (probably?), however that may still not solve filtering vendors by the food categories as there is no direct connections between them. I would probably recommend custom coding this, as it is a very specific case.
The vendors seem to be assigned to the foods (products). So filtering food by the vendors and food categories could be possible, but not the other way around.