Q: Import video to Photo Gallery

To my knowledge synced videos go to the Videos app

you cant do it from your mac however you can off a memory card. If you have the card reader accessory, you take a camera SD card, and in the DCIM folder you put your video in, following the camera naming protocol - an 8 character name, for example DSC_4578.mp4

Then the photos app thinks it's a video shot with the camera and it goes into the photo app.

The iPod needs iOS 9.3 or later

Import photos using Apple camera adapters - Apple Support