Hello OP I also had to dig very very deep with my first DD, it feels like it’s never ending those first few weeks, my DH cut my food up for me and fed me!
Your LO is indeed putting her order in! Your boobs will only make as much milk as requested, not when you have an empty boob, but sucking equals the making of more milk. The problem with topping up now is that your almost stopping your boobs from making a sufficient amount of milk to sustain your baby so that you’ll have to continue to give her formula ans it’ll become a cycle, the suckling will make the milk.
My DD was the same as your little one, my DS was much more efficient and went longer between feeds but my third DS is the same as my DD ... and so it goes.
My only advice would be to treat yourself, get in some snacks and chocolates and lovely drinks, have a bath with LO and get DH to put some fresh sheets on the bed, then climb in with LO and watch box sets. Prop yourself up on pillows and make yourself comfy, have wipes, nappies, spare sleepsuits close by and try and enjoy it.
Your milk only came in a couple of days ago, in another few days it’ll start to plateau and in a few weeks you’ll be flying.
For the leaking boobs I would go bra-less and just fold a muslin cloth over the boob that isn’t feeding to catch the excess, tuck a muslin into your vest as you’ll be feeling tender so having things loose will help. Try and run the shower head over your boobs as often as you can to ease any discomfort. If your nipples are cracking, try and put on a bit of lasinoh but just on the cracks and let the air get to them.
Try and sleep as much as you can with baby, lying on your side to feed is a bit tricky but is a godsend for these long cluster feeds.
www.llli.org/faq/positioning.html
You’ve got this OP 
you can do it!!!