1. if you are torrenting and saving directly to external drive, will it damage the drive?

2. Latest version is messing with the USB drives, coz older NON-smart TV wont play the video unless video is removed to another drive and re-saved to the usb drive

is this correct?

1. All flash media (SSD, USB thumb drives) have a limited amount of rewrites. Using up read and write cycles will slowly wear out the drive finally leading to its death. Comparatively SSDs are high endurance and USB drives are low endurance and they also get the cheapest flash memory possible.
I think if your incomplete-pieces folder is not placed on the USB drive then Tixati might be the most gentle client out there.

2. What you describe sounds like a file system on the drive that the TV does not understand. Please ask elsewhere or in the off-topic section.