Improve crawl speed and php warnings

At first I was glad to see it scanning cause I have a huge database (145.000 media). But…so far “1% (1706/145408) actually treated” in 30 hours of scanning!! This is ridiculously slow.

So what am I supposed to do now for the next two months? Leave the browser window open, or pause and resume in off hours?
Also, my error log is populated with PHP warnings (I run PHP 7.0) like:

[18-Jan-2017 01:26:21 UTC] PHP Notice:  Undefined variable: cum_medias_in_content_index in [...]public_html/wp-content/plugins/clean-unused-medias/ws/crawl.medias.php on line 164
[18-Jan-2017 01:26:25 UTC] PHP Notice:  Undefined variable: percent in  [...]public_html/wp-content/plugins/clean-unused-medias/ws/crawl.medias.php on line 163