When you try to modify a table in Wordpress, it doesn't seems working at all. It's because you cannot override the theme configuration by using simple formulas such as cellpadding or cellspacing.
What you need to do is to try to change in very single cell in the table. For example:
<table><tbody>
<tr>
<td
style="padding: 10px;"></td>
</tr>
</tbody></table>
Have fun!