Re: About to give up
It sounds like your main problem is confidence! Her weight gain is normal, her intake is normal (I know 1.5-2.5 oz seems like a very small amount compared to what formula-fed babies get in their bottles, but remember that breastmilk is digested very completely and formula is not), her nursing frequency is normal, her pee and poop frequency is normal... It's all normal, mama!
The nursing behavior you describe is frustrating- but also normal. Hand-sucking can be a reliable hunger cue in a young baby, but older babies tend to start hand-sucking for fun. They can also go from zero to sixty in a heartbeat when it comes to hunger cues. Both my girls were like that. They went from fine to screaming in a moment, with no intermediate step of hand-sucking or rooting or anything.
Coolest thing my big girl said recently: "How can you tell the world is moving when you are standing on it?"
Coolest thing my little girl sang recently: "I love dat one-two pupples!"