Hi there,
Sam from Moz's Help Team here - apologies in advance for the long response!
1. URLs too long.
URL length and format for SEO is a bit of a balancing act. When considering URLs for SEO you want to make sure that the URL is simple enough to remember and understand for human visitors and that it accurately describes what is on the page.
If your URLs do this job, but are a bit longer than 75 characters, then I wouldn't be too concerned.
You do want to keep you eye out for URLs that are not within this basic structure:
http://www.example.com/category-keyword/subcategory-keyword/primary-keyword.html,
contain long and confusing codes, and are taking a hit in the rankings.
As I'm sure you're already aware, changing URLs is quite painful, as you need to make sure the old URLs are redirected and this adds more moving parts to your site that could cause problems down the line. So, if you're happy with the job your URLs are doing currently, but the tool flags these as too long, I would definitely consider holding off on making changes. It may be that you use this information to make amendments to future URLs, or rethink your site structure as part of a bigger project.
In the meantime you can "Ignore" those issue either by page or by Issue Type through the Moz Pro Site Crawl interface so they don't crop up every week. You can read more about this on our Help Hub.
Here are some resources on URL formating and how to best structure them for SEO:
https://moz.com/community/q/what-should-be-the-length-of-page-url-from-seo-perspective
https://moz.com/learn/seo/url
https://moz.com/blog/15-seo-best-practices-for-structuring-urls
2. Duplicates
Our tool has a 90% tolerance for duplicate content, which means it will flag any content that has 90% of the same code between pages. This includes all the source code on the page and not just the viewable text, so often it's a matter of finding the best answer for the duplicate pages in question.
For instance, often with ecommerce sites, product pages will come up with duplicate content between two colors of the same item, and in that case it's good to use the canonical tag: https://moz.com/learn/seo/canonicalization. If there are two versions of the page that exist - for instance, example.com/subfolder and www.example.com/subfolder - you can put in 301 redirects to the correct page: https://moz.com/learn/seo/redirection. If it's just two pages on different subjects but with thin content, filling out that content with an extra paragraph or two can help.