Accidentally ejected External drive while downloading file, now having problems reading
More than likely, the drive is failing.

There are several symptoms that point to this (downloading of the Torrent is just coincidental, not causal):


The drive "accidentally" ejected.  By itself, this is not an indication of a failure as it could have been any number of factors that caused the drive to eject; from a power failure to user error.  However, in addition to the other symptoms, it lends credibility to the theory.
The drive works for about 10 minutes then hangs the system.  Good drives don't hang your system.  Additionally, if you system is fully functional (no hangs) until after you plug in the questionable drive, it's a good bet that the drive is the issue.  

As a test, try a different external drive.  If the problem goes away, you've (through the process of elimination) identified the issue.
It's a Seagate.  (IMO) Seagate drives are some of the most unreliable devices in IT.   Based on reviewing tech support reports for our departments activities, a vast majority of the hard drive failures were Seagate.  

Though, that is my personal experience, it appears I'm not the only one judging by this PC World article from 2016:  Seagate slapped with a class action lawsuit over hard drive failure rates


Data Protection/Recovery

Your best bet right now is to focus on data protection and recovery.  I have personally used Disk Drill for both diagnostics and recovery and it has worked extremely well.

Additionally, you should 


Make an image of the drive and work off that:

sudo dd if=/dev/rdiskX of=~/Desktop/external_drive.img bs=1M





Stop using the external drive for daily use until you can recover the data. 


Personally, I recommend Western Digital Passport drives.  I have one that I have been using a daily Time Machine back up drives for over 4 years with no issues.  In comparision, I had a Seagate that was given to me I was using to back up my Synology NAS, died about 18 months in; even free, they're (Seagates) not worth the trouble.