First, as far as latching, keep working on it, give it time an if you can, and if possible, visit an LC for pointers. I'm a STM who breastfed my first for 21 months, and I still had issues with DD2. She cried, screamed and wouldnt latch for almost an hour. I dreaded feeding times and even caved a few times and pumped and gave a bottle (maybe 3 times). But my mom and DH sat with me and we kept working at it. I was a day from calling an LC when she just clicked (around 10-11 days) and started latching like it was no issue.
She lost a whole pound by her first weigh in, and only gained a few ounces at 8 days. She didn't hit her birth weight (well 1 oz shy) until 2 weeks. Many bf babies need 3-4 weeks to get to birth weight. I wouldn't jump to formula just yet. Babies get more than you can pump so I would keep nursing as much as possible and giving her time to latch (again an LC will have pointers on what the issue might be).
I would nurse/pump as much as possible to keep building your supply, but your output is pretty normal at this point. But you can also try some of the tips like drinking more water, eating oatmeal, mother's milk tea, etc.
You are doing well, but keep working on it, you'll be surprised that you won't even remember these days when things start working fluently and you can just snuggle in for nursing sessions.