i managed to have the index full width by making my own page with the forum shortcode and page set using full width layout. but once i click anywhere on the forum (go to a section, thread) the sidebar re appears.
That’s because it’s going back to the bbpress.php which isn’t working for you.
try replacing
if (have_posts()) : while (have_posts()) : the_post();
/**
* Find the post formatting for the pages in the post-page.php file
*/
get_template_part('post', 'page');
if(comments_open( get_the_ID() )) {
comments_template('', true);
}
endwhile;
with
while( have_posts() ): the_post();
the_content();
endwhile;
in your bbpress.php file