Ouch, Google will definitely notice. But if you already took a big hit on traffic then this probably would be a wise choice. What i would check before is how much traffic is going to the pages that you've deleted so you know upfront what kind of traffic you could lose again by removing these pages.

With luck though the pages that will remain in place will have more authority as they get better links from across the domain.

Hi Gavin,

Just look at any sitemap that you can find as they'll all look the same and the only thing different would be the URLs in there. I doubt that sites will really have it different from others. You can check our sitemaps for example here: http://thenextweb.com/sitemap_index.xml

I'd say no, duplicate content is usually copying thousand or hundreds of articles of quite some length to another page. But if you are just adding the same content that could help your visitors then don't worry to much about it. If it's good for your users, Google will usually also like it.

Could you share the example here? I doubt it would create any issues as it seems that it's more an issue on the side of most SEO crawlers. A title elemement on an SVG doesn't even get close to being a second title tag

Have both the categories as tags been indexed by Google? Usually you leave one of them out of the indexes of Google to make sure you don't get in trouble with creating a lot of duplicate content and not unique pages.

I agree what is answered above, I doubt that the keywords people will search for include both numbers so then it would be up to you to decide what you're gonna focus on.