You poor thing, that sounds so painful and exhausting. Have you thought about sourcing some additional support from a community-based lactation consultant? They are often available thought the local council or you could source someone privately. I had lots of trouble with DS and found their help invaluable (I went with someone private and found the assistance was better). Alternatively your council might have a day-program for breastfeeding help? The one I went to was almost a full day so they saw multiple feeds. They also provided general tips on settling, etc.
early breastfeeding with my DS was super painful and such a struggle but it generally does get better with regards to pain. I don't have experience with introducing formula for some feeds so will leave that up to others. I know my sister introduced formula top ups from birth (her milk took ages to come in). She went on to phase them out and breastfed until 12mths.