Outsiders view.
There seem to be two problems

1) the songs haven't got notation.
2) the newer songs aren't as popular.

easy solutions to both problems.
1) Render unto Caesar what is Caesar's.
This is a job for a very specific skill. A good transcriber could do half a dozen hymn tunes in hour. Pay him out of church funds. Your local musicians union should know someone who is good and fast.
End of prob.

2) Performing a song is also a very specific skill. To influence an audience to enjoy it, the front people have to know it back to front and back again. they have to know clever little bits and harmonies that they enjoy, to add those flourishes that an audience will get off on. That goes for ANY kind of music.
Take ONE new song that you can agree on. That is enough for one or even two months. Taking a whole book full at once is just plain ridiculous.

stop getting pissed off with each other. its in the nature of things that band members blame each other when things go wrong.

it does no good. think about what your ambitions and hopes were when you started with this band - don't give up on your dreams too easily.

al