The FTP information seems to take me directly to the /eCart/ directory, but the error appears in the /WA_eCart/ directory, so I'm unable to look at it and diagnose the cause of that error.
I'm a bit confused about what you are trying to do on the ecart_questions.php page. Are you trying to only show the related products for the section they are in? It doesn't look like that page is identifying what items are in the cart to determine which checkboxes to display, and the include file wouldn't know which section it is under.
I created a new page: relatedproductsforcat.php
I think you can use that one with code like:
$catID = 1;
and just set the $catID to the category you are trying to display. I updated it on your page so you can see as an example.