You can do it in different ways:

Json Encode

This is my favorite way of passing data/settings/etc to the front-end.

PHP

$obj=array(
    'content' => $post->post_content,
    'title' => esc_html( get_the_title() )
);

Now the button output will be like this:

HTML

<button class="btn btn-primary tag_cnt get_button_more_info" type="button" value="<?=json_encode($obj)?>"></button>

Javascript

(function($) {

  $('.get_button_more_info').on('click',function() {
    var obj = $(this).val();
    obj = JSON.parse(obj);

    $("#myModal .modal-body").html(obj.content)
    $("#myModal .modal-title").html(obj.title)
    $("#myModal").modal();
  });

})( jQuery );