For the invunerable thing, I've used that before. Just edit/make a new template with everything the same just change the health count a bit
About the immobile, I'm not too sure about that. I dont have JED on this computer, I have it on a different one, so I cant check for ya, but if you could, check around with the things flags and see if there is something on unmoveable or something. Thats all I can think of now.
Theres other solutions too for that that I would use if I cant find out the easy way. Like just deal with the fact that if you push a person in real life, they actually might move. If you really dont want them to move, a couple of things to think of. Either put them in a box to where they cant get out of it, but the box is see through.
Or better yet, just thought of it, make all of the sectors around the little sector you put the guy in, be flagged with "No AI" or something like that. They wont be able to walk into other sectors. I dont know if there is another technical way, but that should work. Atleast it would for me....