How to place multiple blocks in one column in bootstrap theme
This approach might suit your case.

Create 2 new regions in your template info file and render them in your page.tpl.php 


  If you are using a bootstrap subtheme, this file will be located in
  siites/all/themes/bootstrap/templates/system so you will have to copy
  it and put in your templates folder under you subtheme folder.
  Remember to clear the Theme Registry cache after this.


So I would do this like below 

info file

regions[main_block] = 'Main Block Region'
regions[side_block] = 'Side Block Region'


page.tpl.php file

&lt;div class="row"&gt;
  &lt;div class="col-md-7"&gt;
    &lt;?php print render($page['main_block']); ?&gt;
  &lt;/div&gt;
  &lt;div class="col-md-5"&gt;
    &lt;?php print render($page['side_block']); ?&gt;
  &lt;/div&gt; 
&lt;/div&gt;


After go to the blocks admin interface and select the blocks to show on the correct region. Also for the Side Blocks render all three blocks you need in the Side Block Region and use the correct weights to sort them as you like.