Hi Gina -

Great questions here. Some of these you should worry about, others are just notices and not necessarily an issue.

Fix the 4XX errors if those pages have links, or have a 404 page that redirects users. 404s are not always bad, but if the user isn't supposed to end up there (ie your product page is expired), then redirect.

Don't worry about the duplicated meta descriptions on archive pages, but do think about if these pages are needed. Ayima had a good post on pagination recently - http://www.ayima.com/seo-knowledge/conquering-pagination-guide.html

Same as above with the title tags on paginated archives.

Rel-canonicals are fine. Once again, just notices that they are there.

Did you implement those 301s? Moz notifies you of them because they might pass less link equity than straight links, but 301s are not bad.

What do you mean by "These are blog articles but only some of the posts. Don’t know why we are generating this for some and not all. And half of them are for the exact same page so there are really only 4 originals on this list. The others are dupes." It seems that this may have been implemented manually on your side, though I don't know how All In One SEO Pack handles it (I use Yoast).

Absolutely no harm at all.  Do you have an index sitemap that you list all the sub-sitemaps from? If not you should do that as well just for sanity of sitemap management.

I definitely agree with Logan. The max for an XML sitemap for Search Console is 50,000 URLs, so you won't be able to fit all of yours into one.

That being the case, divide them into different sitemaps by category or type, then list all of those in one directory sitemap and submit that. Now you can see indexation by page type on your website.

Finally, I have to ask why you are doing this with a third party tool and creating a static sitemap as opposed to creating a dynamic one that can update automatically when you publish new content? If your site is static and you're not creating new pages, then your approach might be ok, but otherwise I'd recommend investigating how you build a dynamic XML sitemap that updates with new content.

Cheers!

Hi there! Great question and one that has perplexed SEOs for years.

You are indeed right that one of the best ways to rank the page over the PDF is to put some of the PDF content on your page and do other best SEO practices (eg build links to the page, have a better optimized title/etc than the PDF itself). It is also possible to put the rel-canonical in the header of the PDF - https://moz.com/blog/how-to-advanced-relcanonical-http-headers

Finally, if you don't want your actual PDF showing up in the search results, consider a) blocking it in the robots.txt and then b) requesting the URL be removed from the search index via Search Console.

Good luck!