It sounds like a major source of tension is breast feeding. Have you looked into hiring a breast feeding coach?

Another note is that babies in my experience are oddly perceptive to the parents being stressed out or tense (not in any sort of damaging way). Try to do anything you guys possibly can to relax... massage, walks, whatever, etc etc and you may find she feeds better and is generally easier on you guys.

Lastly your situation is more common than unique. At the worst you'll muddle through it and look back and say thank god thats over. It feels like torture now but you guys will be fine - every couple Ive known in your situation goes through some form of this with a new child.