Welcome to the Q&A Forum

Hi, I can't recommend the ScreamingFrog enough! The free version has a limit of 500 pages, so you will need a license. With such a large site it it recommended to check on the crawl progress to ensure there are no crawl 'loops' If for example it turns out that a calendar on a page counts as a link for every day then the crawl will likely never finish! Luckily you can fix such things by creating a URL Exclude rule and the re running the spider. Kind Regards Jimmy

You can delete it as long as the 301 redirect still occurs. 301 signals to search engines "hey, this page has permanently moved to this new location so whatever signals you had for this page, send over to the new location and ignore any content on the old url" So be sure to set your 301 redirects at the server level (via htaccess on Linux or via IIS on Windows servers) if you plan on deleting the page. I know yoast SEO plugin has an option to redirect to another page in their settings for the post/page (in this scenario, you wouldn't delete the post/page).

I don't think the SEO plugin will assist with that but there are a number of plugins that will help. I recommend https://wordpress.org/plugins/broken-link-checker/