Increase 10 post limit per page

It seems your theme (or one of your plugins) has reduced the query to 10 posts per page.
Otherwise, changing the option in the Settings page has to change the number of posts per page.

Check code of your theme and remove posts_per_page parameter of queries (If queries have been modified, and this parameter was set).

To have all posts of your blog in one page, you have to set posts_per_page parameter of queries to -1.

To make any custom queries obey your settings, you have to set the posts_per_page parameter in query arguments to get_option('posts_per_page').