Use form-submit to display results table on page
I don't think you can return a themed table on form submit. Instead, what I suggest is to use $_SESSION variable to store the form field values to query the database and redirect to a URL. In the callback function of the URL query the database and return the themed page.

Example: 

function mymodule_myform_submit($form, $form_state){
   $_SESSION['somevar'] = $form_state['values']['somefield'];
   drupal_goto('someurl');
}


And in the URL callback function get the value of the session variable $somevar = $_SESSION['somevar'];