Should be able to do that with Jellyfin, no Plex/Plex Pass needed (if you really want to use media software for this).
That said I suspect your current method with creating a torrent to share is much more resilient when dealing with choppy internet connections. With Jellyfin/Plex it's more of a direct download situation, not sure if either can resume broken downloads.
Yup. The Tixati torrent client is also developed by the same dev team (mainly Kevin Hearn I believe).
I think that the timeline was WinMX, then Tixati, then Fopnu, then DarkMX. (Tixati / Fopnu / DarkMX are still actively developed and updated)