You can play the B/F# in a couple of different ways. This way is how it sounds like he
it in the song:
B5 : 221xxx
But, if you feel like adding in a nice note (a bit tricky though), play it this way:
B5 :2214xx
and use your pinky for the last note.

If neither of those suite you, you can always play it this way:
B5 : 2244xx

Just make sure not to hit all those high notes, as the "proper way" to play the chord
be... at least not in the acoustic-guitar verses, because it's only the bass notes played
the song.

Lastly, in terms of ending the choruses with the E major to E minor switch, you can play
chord to the next, or, to sound more like the song, you can strum the individual notes
this:
E-------------------------------- | 
B----------0------------0-------- | 
G--------1---1--------0---0------ | 
D------2------------2------------ | 
A-------------------------------- | 
E-------------------------------- | 
       E5 major      E5 minor


Enjoy...


B5                       E5
Keep a little organ in you, now.
B5                       E5
Sing about the promises you found.
B5                                 E5
Keep it up, ?cause no one likes it down.
F#5                     B5
Get lost in the overrated down.

B5                       E5
Keep a little organ in you, now.
B5                                   E5
Sing the song that filled your mother?s house.
B5                             E5
Little Thomas, he just wants to doubt.
F#5                          B5
So sing a song you never sing aloud.

Chorus:

Ab5       E5      B5
Oh yeah, yeah, yeah.
B5
Don?t you wanna be the last one standing out?
Ab5       E5      B5
Oh yeah, yeah, yeah.
B5
Don?t you wanna be filling up the dark?
Ab5        F#5   C#5
Oh yeah, yeah yeah.
            E5            E5
So just sing it loud, once you think you?ve figured out?

B5                 E5
How you grew up so fast,
B5                       E5
Hoping to the face inside the glass.
B5                                    E5
You kept the beat, but you always came in last.
F#5                                     B5
And I?m the kiss, you?ve been keeping secret stashed.

Chorus:

Ab5       E5      B5
Oh yeah, yeah, yeah.
B5
Don?t you wanna be the last one standing out?
Ab5       E5      B5
Oh yeah, yeah, yeah.
B5
Don?t you wanna be filling up the dark?
Ab5        F#5   C#5
Oh yeah, yeah yeah.
            E5            E5
So just sing it loud, What I?ve never figured out.


*Guitar Solo*


Chorus:

Ab5       E5      B5
Oh yeah, yeah, yeah.
B5
Don?t you wanna be the last one standing out?
Ab5       E5      B5
Oh yeah, yeah, yeah.
B5
Don?t you wanna be filling up the dark?
Ab5        F#5   C#5
Oh yeah, yeah yeah.
            E5            E5
So just sing it loud, What I?ve never figured out.


B5                       E5
Keep a little organ in you, now.
B5                       E5
Sing about the promises you found.
B5                                 E5
Keep it up, ?cause no one likes it down.
B5                       E5
Keep a little organ in you, now.
B5                       E5
Keep a little organ in you, now. (Continue and fade until end)