rewrite rules help needed

Hello everyone,
i recently was asked to upgrade a website where some of its pages had a (for me at least) strange set up. The previous developer did a custom post type member and created some custom pages to do some functionality for the type (search, group by country etc).He also added some rewrite rules todo that, like so

#Membership
RewriteRule ^membership/?$ wp-content/plugins/_custom_pages/membership/index.php [QSA,L]
RewriteRule ^membership/country/([^/]+)/?$ wp-content/plugins/_custom_pages/membership/country.php?slug=$1 [QSA,L]
RewriteRule ^membership/country/([^/]+)/page/([^/]+)/?$ wp-content/plugins/_custom_pages/membership/country.php?slug=$1&page=$2 [QSA,L]
RewriteRule ^membership/country/([^/]+)/([^/]+)/?$ wp-content/plugins/_custom_pages/membership/member.php?slug=$1&ID=$2 [QSA,L]
RewriteRule ^membership/all-members/?$ wp-content/plugins/_custom_pages/membership/all.php [QSA,L]
RewriteRule ^membership/all-members/page/([^/]+)/?$ wp-content/plugins/_custom_pages/membership/all.php?page=$1 [QSA,L]
RewriteRule ^membership/all-members/([^/]+)/?$ wp-content/plugins/_custom_pages/membership/member.php?ID=$1 [QSA,L]
RewriteRule ^membership/search-our-members/?$ wp-content/plugins/_custom_pages/membership/search.php [QSA,L]
RewriteRule ^membership/search-our-members/page/([^/]+)/?$ wp-content/plugins/_custom_pages/membership/search.php?page=$1  [QSA,L]

The problem is that there are also other pages that are nested under the membership page but are not physical pages in that plugin and now when someone tries to access them they get a 404 error, for example /membership/members-qa-corner/

I am trying to fix this but rewrite rules have never been my thing and i have no idea how to fix it, any help? ??