wp_dropdown_pages with tax_query clause

Amusingly, the codex for wp_dropdown_pages includes this:

It is possible, but not confirmed, some of the paramters for the
function get_pages could be used for wp_dropdown_pages.

This must be at least partly true as I assume your use of post_type as an argument is successful. That being the case, give exclude a shot too.

In your companyList loop, build an array of post IDs to exclude:

$name=$post->post_title;
echo '{ value:'.get_the_ID().', label: "'.get_the_title(get_the_ID()).'"},';
$exclusions[] = get_the_ID();

Then just throw that argument into your wp_dropdown_pages:

$args = array (
    'id' => 'house',
    'name' => 'house',
    'echo' => 1,
    'post_type' => 'house',
    'exclude' => $exclusions
);