Blog Extension for Magento 2 - All Questions

Due to a significant difference between Magento 1 and Magento 2 branches, the extensions for M1 will not work in M2.
However, the owners of the extensions by Aheadworks for Magento 1 can get 25% discount on purchase the same extensions by AW for M2

Discus is being used as a comments management tool in our Blog M2, but this is a completely separate solution maintained by their team.
As I can see in their guides, Discus supports import from XML.
As for our Blog for Magento 1, it doesn't have export functionality, to my regret, so to export comments additional migration work is required.
However, your developers are free to perform custom migration work since the code of our solutions is open, or it is possible to take advantage of our additional Migration service. I would suggest that you check once again that "Disqus Forum Code" value in our Blog settings contains a correct UniqueDisqus URL.
As per Disqus, your unique Disqus URL should be: shortname.disqus.com (where "shortname" is the one you've set in your Disqus per this store).

You may want t use 'Use Canonical Link Meta Tag For Posts' option as long as it fits your requirements.
You can read more about 'Canonical tags' in the User Manual, available on the following link:
https://aheadworks.com/resources/blog/user-manual-blog

Since Blog M2 has a migration tool, blog posts transfer can be done according to our User guide.
https://aheadworks.com/resources/blog/user-manual-blog#migrating

It is possible to set the "Number of Posts to display" upon the "Recent Posts" widget adding in Content > Elements > Widgets > Add a Widget

Comments in our Blog can be disabled via the "Comments Enabled" setting under Stores> Configuration > AHEADWORKS EXTENSIONS > Blog > General. As for multi-store, the extension can be configured separately per Website or Store View scope.

Currently, there is only the Recent Posts widget that can be inserted into CMS block or page via native Magento means.

However, your developers are free to customize the widget and modify the layout of the blog list page via additional custom development since the code of our solutions is open.

You may just need to select the required 'Store View' for your French language post via your blog post configurations. Also, I'd suggest that you check and make sure that you are using the most recent Blog version. The latest version provides an option to save posts with the same URL key for different store views.
You'll also find basic configuration instructions in the User Manual here: https://aheadworks.com/resources/blog/user-manual-blog The extension doesn't currently provide any other additional automatic redirect options for blog posts for different store languages, out-of-the-box.
However, you may want to try and configure redirects manually for your system on your side or order our customization service so we could work out a custom solution for your requirements.

Currently, it is possible to create a separate copy of Blog per store view level but out of the box, there is no possibility to have two blogs in one store view, to my rerget.
However, I would suggest organizing recipes and other articles as separate Categories of Blog.
It is possible to create them in Admin > Content > Blog by Aehadworks > Categories
It is always possible to refer to our User Guide for more information:
https://aheadworks.com/resources/blog/user-manual-blog#:~:text=for%20Aheadworks%20Blog.-,Blog%20Categories,-Categories%20Grid
Also, if yo would like to implement two separate blogs in one store view, perhaps it can be done via additional customization.