You don't get what? The prereqs? I'll clarify - there is no global prerequisite for service depots and you have listed all the global prereqs.
As for negative damage... I'm sure giving things negative damage is buggy in YR, but you could try giving the animation (Yuri's eyes in a cloud) Damage=-xxx. That's a good idea actually, the Psychic Dominator controlling enemies and healing them too... but it will also heal the buildings you use it on - you will have to be careful with this (unless your intention is for it to heal buildings). But I'm pretty sure this won't work anyway.
^^^ Yeah, that's what I want to know. A lot of questions can be answered by reading the INI Guide. If I had glanced at the guide before my last post, then my last post would look something like AG's last post