URL length does not have much impact on how Googlebot crawls.
Changing your URLs will have the biggest effect. Googlebot will forever come back and crawl your old URLs. You will need to implement redirects to the new URLs and maintain those redirects indefinitely. If you change all your URLs, this can significantly increase the number of URLs that ...
No, it won't.
All you need to focus on is to make things easier for the end-user.
Everything else doesn't matter anymore.
Google's algorithms are very evolved and what's good for the user is good for robots and ultimately for rankings.
This certainly looks like a mistyped URL in the links on pages /blog/page/12/, /blog/page/13/ and /blog/page/14/. On those pages look for a link like the following:
The erroneous single back curly quote ’ at the start of the URL will trigger the user-agent (...
As @closetnoc said above, no, you can't make it appear as if you only have one blog when they're all subfolders on the same top level domain, at least as far as search engines are concerned. Assuming that you want your TLD as well as each of these blogs in the search indexes, you'll have to let all of this be crawled and indexed. Thus, anyone doing any in-...