Indeed it is "I'd give the moon and the sun 'fore I live", it might express that he put "giving her the moon and the sun before even his own life".
That is, his utmost priority is to give her the moon and the sun. Well, it´s not grammatically easy to figure it out, but with music you have to "crack the code" from the context.
'fore - the ' means an ellision of a word. That is rather common with music, and sometimes with literature as well.
So, you can see "ne'er", the elided form of never, "gonna" the elision of the form going to, and so on and on.