Might indicate a very slow connection (for whatever reason, slow Tor entry guard or otherwise). To get around that you can try to increase the timeout. Currently only possible by manually editing with root rights.
kdesudo kwrite /usr/bin/update-torbrowser
Search for curl_download_max_time= and increase the timeout (in seconds).
Unlikely. I think we need a wiki entry for this, but no, for any serious malware it would be a disgrace of the malware author if you could spot it through this.