What you’re trying to do with the video is exactly what Post Formats were created to handle.
Add this to functions:
add_theme_support( 'post-formats', array( 'video' ) );
And then this to handle your Read More link:
if( !has_post_format( 'video' ) ) {
echo '<a href="' . get_permalink() . '">Read More…</a>';
} else {
echo '<a href="' . get_permalink() . '">Watch the Video…</a>';
}