#1
Can anyone give me any tips and tricks on how to maybe get the barring of my index finger to make every note on that fret come out smooth sounding? I've been (if you look at the tab it will make more sense) just putting my finger on the 4th and 9th frets on the D and G strings for the first two parts of the verse, but that still leaves the 3rd part with the 7th fret having to be barred. I can get the top notes right, but they don't sound good when I play around the middle of my finger.

Also switching from some of the 'chords' to the next seems to be a problem for me. I can play all of the parts by themselves, but when I try to play with the song, or just all together I mess up a good bit.

Thanks.

http://tabs.ultimate-guitar.com/j/john_mayer/edge_of_desire_ver3_tab.htm

Here's a link to the tab for reference.
#2
John typically plays with his thumb wrapped around the neck onto the 6th string ala Hendrix. Try some of the barres that way.
#4
The way I've seen him play it he does do a slight bar. Maybe not full on, but a little it looks like.