If you give Stealth Boys to companions will they use them if you use them? I'm guessing no. Oh and why in the hell can you heal ED-E USING STIMPACKS?

Because E-DE Is Chuck Norris' Computer.

I don't think they use stealth boys.
As for the stimpacks, I have no idea. Maybe ED-E is part organic?

On a related subject, I've been wondering how stealth works when you have companions around? I've been traveling with Boone and ED-E for a while, Boone goes into sneak mode when I do, but I'm guessing - and hoping - my stealth skill level (50 at the moment) is the only factor in whether enemies will notice any of us, including ED-E hovering up there in the air?