Here to give some encouragement...
I was blessed with a 9.6oz ds, although I was told to supplement in the early days, as he lost weight I fought with the hospital and continued to nurse. But it happens my friend when thru the same thing, and she unfortunately got the wrong advice and stuck with the formula. My opinion is to cut back on the formula as much as possible, the thought is, less formula to eat, more breastmilk to eat and produce. Keep in mind all babe's will lose about 10% of their body fat upon birth. They were born with extra reserves. I know how distraught you are over this. YOU CAN NURSE.... I had the same emotions, I thought my babe wasn't getting enough and I just sat there with my feet up, topless watching tv with him laying on a boppy. I drank the Mother's Milk tea, immediately after his birth and suprisingly my milk came in in unde 48 hrs, and that was with a c/s w/ complications. I know you said you had another little one at home, so relaxing in front of the tv may be difficult. I would suggest putting your dd in a sling, exposing your breast, this will make it so readily available to her and you can still interact with your toddler. Also it may take some of the pressure off both of you to get her to nurse, as it will be a more relaxed approach..
Another thing was sister had me do which I thought was crazy, but hey she's a fellow mdc member.... I nursed on one side for two hours. Say ds would start eating at 10:00, no matter what I would switch him at 12:00. If he was up straight then he'd have the same side, say if he slept for past 12:00 and only nursed on that side for 10min, I'd still switch. My ds who lost the standard 10%, ended up gaining 10oz within 1 week.. My ped was even shocked and I still have an overabundance of milk.
Honestly within time, you will look back on this and be so much calmer. It does get so much better, believe me, I had the highest-needs nurser, you just got to say I can do this another day and keep going. No matter how well you raise your babe in the future, there is nothing more healthier than breastmilk.
**A great book to also have on hand is Dr. Sears's Breastfeeding Book...
Best of luck...YOU CAN DO THIS