I believe the PC version of HereSphere still lacks passthrough support for technical reasons. You can use the on-headset version of HereSphere, but you’d need to get the videos to be accessible - either over SMB, DNLA, xbvr, or by manually copying video files to the headset storage.
Since you already use the timestamp server you can access that from the headset, although you’ll need to enter IP addresses for your headset in the timestamp server app.
There’re a few tutorials in the How-To section here on EroScripts that will help.