james.d

No. 1 has been self-resolved, too.
A thumbnail size can be changed in “Media Settings” page in your WP admin (Settings > Media). Once updated, FB thumbnail’s dimension will be adjusted accordingly.

As for changing thumbnail’s size for older posts, this can be beautifully done by using “Regenerate Thumbnails” plugin.

Cheers.

Resolved it by myself.
Can add the following in any css file.

.fb_edge_comment_widget {
  display: none !important;
}

Mine is pretty simple. Somehow only works with “ugly permalinks”. Thank you for your help.

<div class="navigation">
<div class="alignleft"><?php previous_post_smart('%link', 'Previous', true); ?> </div>
<div class="alignright"><?php next_post_smart('%link', 'Next', true); ?> </div>
</div>