I don't have any useful advice, but I wanted you to know that I have been following your threads and I'm rooting for you! I agree with Carol that you shouldn't stress unduly over a single 1-week weight check. Babies don't always read the textbook that says they gain at a steady rate.
I know that you and your nursling have already fought your way through several significant challenges, and that you continue to deal with a lot of pain that limits you. I admire your persistance and want to reassure you that it is all worth it.
You mentioned the possibility of pumping, and recognizing that this would deprive your daughter of the comfort she gets from nursing. If you need another reason to persist with breastfeeding to whatever extent you are able, I would remind you that breastfeeding is the most efficient way of delivering the specific antibodies that your daughter needs, when she needs them. When she nurses, she exposes you to whatever is in her system, and within hours, the specific antibodies to help her fight off those germs start showing up in your breastmilk. It's an amazing process, and one that works less effectively when mediated through a pump and bottles.
I also wanted to reassure you that your perfectly normal responses to the chronic pain you deal with are NOT causing your daughter to undereat. If she wasn't getting enough to satisfy her (both milk in her tummy and time at your breasts) she would let you know very quickly. She is probably taking in more milk than you realize during those feedings when you think she's not eating well. You are nursing on cue, avoiding supplements and artificial nipples. She has free access to the breast, her diaper output is good, and she's usually contented after a feeding. The breastfeeding is working -- believe it!
Keep us posted; I'll want to hear how you two are doing.