This is one of the reasons I don't like lamps - the positioning is really difficult. It has to be close enough to cast enough light, BUT it can't be anywhere in your field of vision because it will mess with your perception, AND it can't be anywhere that will reflect glare on your screen, AND it can't be anywhere that it casts shadows on your screen.
I don't know what to tell you specifically. You'll have to play around with positioning and see what is the least worst position.
Not necessarily.
If the existing bulbs aren't too old, hopefully you'll be able to find some printing on them to tell you what temp they are?