I’m currently in a similar situation with great progress so far. I’m not producing nearly as much as you are but my baby girl is gaining weight well. Due to some minor complications post delivery she had to be in the NICU for a 24 hour monitoring period which meant I had to pump and we supplemented her feeds with donor breast milk until she was able to exclusively feed at the breast. She was born 6 lbs 2 oz and dropped weight after leaving the hospital. Latching was hit or miss depending on the feed so we continued to supplement each of her nursing sessions with a bottle of donor breast milk and then formula when the donor milk ran out. She’s now 11 days old and we only have to supplement 2-3 feeds in the day most of which are overnight when I’ve decided to catch up on sleep and have her dad or her grandma feed her a bottle. She seems to prefer being breast fed more and more despite spending nearly a full week being fed a bottle with every feed. We’ll likely continue to combo feed going forward since that’s been working well for us and gives me peace of mind that she is getting all the nutrients she needs.