Re: Too much and too little
Hang in there! It gets easier, I promise. Everyone has to find what works for them, so of course do what works for you, but I'd caution you against following any "rules" too closely when it comes to timing feedings. Feed the baby when she's hungry, even if she gets impatient with your slow let down. She should learn to suck so that she stimilates the let down and it sounds like she just hasn't yet because she hasn't needed to so far, what with your overactive letdown. You might try giving her more time to figure it out on her own without helping her. My son went through a phase too where he'd pull off frequently to fuss, but I just kept letting him get back on to nurse and eventually our bodies synced and he stopped fussing during feedings. Remember you don't always have to actively fix things- sometimes they will even themselves out.
if you really feel you need to do something though, you could try pumping before she nurses to get your flow going. Assuming slow let down is the issue, that should help. And it wouldn't necessarily cause an increase in supply since you aren't getting milk, you are just getting yourself to the point of letdown. If you do that, a quick suction (like a baby sucking frantically) works best to stimulate let down.
As far as wanting to be able to get away/have DH feed baby etc, those are normal desires so don't feel bad about it. At this point you should still be pumping when you miss a feeding, but going out for a few hours here and there should be OK. It would be best to pump some EBM for those times rather than giving formula though. That way you aren't sabotaging your supply.
It sounds like you are doing a great job so far, mama. Don't stress too much about it and try not to overthink it.
“We are not put on earth for ourselves, but are placed here for each other. If you are there always for others, then in time of need, someone will be there for you.”