YES! Your second guess of "CATHEXIS" is correct! Here are the explanations...
1. The second of two episodes this appears in... This particular hairstyle of Janeway appeared in the previous episode, and once again here. Never again.
2. Reverting back... When possessed Tuvok shuts down The Doctor, the command codes reverted back to her.
3. We don't see this setting often... Possessed Tuvok uses his phaser on wide beam and knocks out the entire Bridge crew. We very rarely see this phaser setting in action.
4. First appearance of this character... Lt. Pete Durst first appears here, then is killed in the very next episode.
5. Better after practice... Chakotay said he got better at controlling movements of those he possessed after doing it multiple times.
6. A shuttle was used... Chakotay and Tuvok's mission had them use a shuttle.
7. First time this procedure was done on the ship... This is the first time the warp core was ejected in VOYAGER.
8. This wasn't required later in the show... Janeway says ejecting the warp core required a command level authorization and Torres couldn't do it, but she is able to on her own in season 4.
9. It has no engines... The ion trail indicates a ship that has no engines.
10. Saves the day, but not really this person's episode... Chakotay saves the day, but except for the end, he only appears comatose on the biobed.
11. A lengthy procedure... The Doctor says the procedure to revive Chakotay would take hours to explain.
12. Attacked often, apparently... Janeway surmises Tuvok keeps getting attacked and wonders why.
13. Before Seven of Nine comes aboard... This is a season 1 episode.
14. A dark cloud over there... The nebula is a dark cloud.
15. A map... Chakotay's medicine wheel has been altered to serve as a map to get the ship out of the nebula.
16. Nourishment... The Komar intend to use the crew as food.
I ran out of obscure clues and started to go more obvious. You got it, JP. Your turn.
(And thank you... I don't know if I had any other clues left to give except say it was a season 1 episode. Maybe I make these clues a little too difficult...)