White screen when activating plugin that sends form via WordPress

you should remove:

require('http://solutionsagencia.com.br/comparasaude/wp-load.php');

and use:

require(ABSPATH.'wp-includes/pluggable.php');

p.s. I advice you, these executions should be hooked in ‘init’, like:

add_action('init', function(){

    $para = "[email protected]";
    $assunto = "Assunto" . $nome;
    $conteudo =
    "<b>Nome:</b> {$nome}" .
    "<b>Email:</b> {$email}" .

    $headers = array(
        'Reply-To' => $name . '<' . $email . '>',
    );

  $status = wp_mail( $para, $assunto, $conteudo );

  remove_filter( 'wp_mail_content_type', 'set_html_content_type' );

  if ( $status ){
    echo "sucesso";
  } else {
  }

});