Well, honestly I don't think I can add anything useful as far as how to word or organize the legend information. You got it all pretty good with this last update.
Having the Admin office/Security office/Scientist office bonuses organized into boxes goes a long way toward clearing up the confusion there. It makes it pretty obvious how the bonuses work. Only thing I see that could maybe use some clarification is the Head of security office with Security +2. I'm pretty sure you're talking about Security 1 and Security 2 terits, but perhaps spelling that out would be better? I'm not sure on that, maybe most people would understand, but there are bound to be a few people out there who wouldn't understand it right off the bat. That one is pretty subjective, so you can take it or leave it, no biggie.
One question about those bonuses. Are they cumulative? If you hold the Head Scientist office and, say, the Test subjects holding cell for a +2, and then take the Test area 2 for a +3, do you end up getting +5, or does it only give you whatever the highest one you hold?
I like the way the gun/bullet bonus info is organized now. It's fairly obvious how it works now.
You've got a few minor typos in the legend, not important right now, but figured I'd point them out so you can fix them. Quaters should be quarters (unless you're from Boston), Conferance should be Conference, and I think that is it. That's all I noticed.
As for another weapon/useful item...I quite like the sniper rifle idea and having it able to bombard, etc. However, I also am not sure that it work out. Assuming it's placed in a room (or where ever, that part isn't that important), how would you know which terits it allows you to bombard from? Would it be any terit you hold that has sight of 2 or more touching terits? Or what? I mean, I love the idea, but I feel like it would probably be pretty hard to spell out how it works, what it can do, and actually have that in place on the map. Plus, it might just make it too easy.
I don't know. If you can figure out a way to successfully implement it and explain it in the legend, then I say go for it. It would add a lot to the map, and goes with the theme wonderfully. One issue may be with xml. I don't know all that much about it, but I figure it might be hard to make a territory only able to attack one territory away unless you hold a certain other territory, in which case that first territory can now bombard so many territories away. But you would know better than me if that is possible within the current xml.
If you can't get that to work, then really any of the others would probably work. In keeping with the theme of a laboratory, probably either an axe (fire axes), potted plant or Molotov Cocktail (there are bound to be all sorts of chemicals around that could be used to make one of those, assuming the absence of alcohol) would be the best fit, most realistic. I can't imagine a sword just laying around a laboratory. Well, then again, rocket launchers aren't common sights either, I suppose, so I guess really any of them would work.
But it would be cool to have something that you could do something cool with, like you're thinking about doing with the sniper rifle. Not just another weapon for another bonus, you've got plenty of bonuses, but something that allows you to do something really cool and interesting not possible otherwise. Like if you have the Molotov Cocktail, you could use it in the hallways to clear out the infected, thus eliminating the decay each round, or something else like that. That probably isn't possible with the xml, but you get my drift.
I like where this is headed. Keep it up!