1. - A is the IV in the key of E. B is the V.
I was going to google the other two questions but I felt that was cheating.
PS. Mr. Charlie, I'm incredibly interested in open tuning lessons. I'm tired of learning songs. I've tuned an acoustic to open G. The slide feels comfortable on my pinky. And so I've played the 3rd, 5th, 7th, 12th fret a million times and can fake some crap, but I'm ready to learn real shit. I've listened to nothing but the delta blues the last 4 or so months. I can hear it in my head, then I go to play it and I comes out sounding like bad George Thorougood. Makes me sick. Then frustration mounts so I go back to playing Zepplins That's the Way and telling myself, I'm getting better.
Ugh... frustrating....
Slide is humbling, the technique is so easy, but the feel and touch required and getting all those obnoxious sounding notes to flow well and not to sound so obnoxious takes practice. It still humbles me and leaves me frustrated after 30 years.
Music is so fk'd up in that manner. You can spend months or even years on a technique and then once you conquer it, the satisfaction only lasts a few minutes and the bar of achievement is raised again and it's on the the next frustrating thing. It doesn't matter what level one is, this is a constant. Always striving to be better.
Find good youtube vids on it, if you're anything like me seeing the grips and such, help dramatically. Other than that practice, practice, practice. 10,000 hours for mastery, the more you do it the closer you get.
Only thing I can say to help is to really pay attention to your gliss. Play it very slow at first and get the gliss down pat - make sure it flows evenly then speed it up. And, always record yourself and listen, it helps.
Just in case not knowing where you're at (you probably already know this) and hoping I don't offend: you are using a backing finger to quiet the slide, right? I use two most often.
This picture is the correct technique, notice the forefinger resting on the strings behind the slide. It makes the notes much smoother..... cuts the noise.
Also, I've found using the slide on the pinky on Open G and A, and using the ring on Open D and E make things easier. This guy is using it on his middle and that only gets in the way.