Hi Sandra, don't worry about 404s volume because they won't hurt your rankings.

About your issue I understand that you want to be really clear with your users and don't hurt their experience on the site. So create a custom 404 which changes its content depending of what page is returning it. If it's one of your old product you can return a message or an article of why you decided to remove them and propose some alternatives. For all other errors you can just return a search box or related products to the one you lost.

301 IMHO are not the way to go, if an url is gone it has not being redirected anywhere, so a 301 will result in a bad UX 99% of the time.

You can export your database to an excel spreadsheet, then you can retrieve the url based on your ids in database.

After you have your list of urls you can both do a crwal using screamingfrog or xenu and join the two lists with a vlookup or you can simply retrieve your title and meta description using seotools extension for excel from nielsbosma.se

this is one of the few things where google has a pretty clear statement:

"If you think a content is relevant to your users you should always make it clearly visible"

If you think about that it makes complete sense, if someone searches for a content and clicks on a result they expect to see that text, if that is hidden somewhere they won't consider that result relevant for their search, and that's what google do not want to happen.

I have to agree that the 500 words content still works for the long tail, so I would say, keep your important content at the top of the page and reference other supplementary content at the bottom or at the side but always try to make it visible.

You can see Google standing on Barry Schwartz latest article on google discounting tabbed content

As an addiitonal thing it's totally safe to hide some content on your mobile version if you've a responsive website for improving user experience, as far as that content is clearly shown in your desktop version.

hoep this helps

That could be completely normal. Google sends a warning because you're giving conflicting directions as you are preventing them to crawl pages (via robots) you asked them to index (via sitemap).

They do not know how important those pages may be for you so you are the one that needs to assess what to do net.

Are those pages important for you? Do you want them to be in the index? if that's the case change your robots.txt rule, if not then remove them from the sitemap.

About the previous answer robots text is not used to block hackers but quite the opposite. Hackers can easily find via the robots txt which are the pages you'd like to block and visit them as they may be key pages (ex. wp-admin), but let's not focus on that as hackers have so many ways to find core pages that it's not the topic. Robots txt is normally used to avoid duplication issues and to prevent google from crawling low value pages and waste crawl budget.