That warning is normal when Tor cannot connect to other nodes (which it shouldn't be able to if networking is disabled).
The problem with Tor rendering the HTML file is a bug with the version of Tor in the most recent version of Tails. There is a link to an older version of Tails that doesn't have this issue somewhere in the comments on that post. Since you're using it offline, using a slightly older version really won't matter much.
If the problem is caused by Tor, wouldn't it be easier to install a different version of Tor or a different browser on the persistent volume (not sure if this is even possible)? Or is there a security risk involved when solving it this way?
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