What kind of speakers are you using?
From what you've described, it sounds like you're using passive speakers with no
power amp. To use the balanced output, you either need powered speakers or a power amp for your passive speakers.
I'm not sure what the difference is of using the headphone out for speakers, but I believe there are differences in eq so your monitoring won't be accurate. Mind you, you could just use headphones.
The 'crackle' you describe just sounds like clipping. If you recorded all the guitar tracks right up to the red on individual tracks, playing them all together will make the master clip. Try turning down the individual tracks and keep an eye on the master level until it doesn't hit the top of the red area.