Many feed stores have antibiotics. Penicillin G Procaine is a very common one, and they'll usually have one or two others.
You have several choices:
Take the doe to the vet Friday, treating her with compresses and willow until then if you have willow.
Treat the doe yourself starting Friday, with antibiotics you buy at a feed store. Compresses and willow until then.
Put the doe down.
I think you do need to try to get the kits to nurse from her, but I wonder if the inflamed teats might give only pus at this point? It sounds pretty advanced. If they're nursing only from the soft ones, that may be the reason.
It's possible that she's in so much pain, that she's not producing much milk at all anymore. The infection is self-perpetuating, though, and must be treated (it really does sound like infection to me).
The formula you are using might work. I say "might" because it is cow's-milk based. Cow's milk is often not well tolerated in rabbits (or even kittens, for that matter), and frequently causes diarrhea. Goat's milk replacer (goat formula), fresh goat's milk, canned goat's milk, or the formula Zass pointed you to that uses canned goat's milk, are more likely to work well for your kits. The key to that formula is that it is highly concentrated. Baby rabbits don't eat a lot, but they grow fast. That means their mama's milk is super-nutrient-packed! The formula usually needs to be, too, though some have raised baby rabbits on straight fresh goat's milk. Not everyone has had luck with that, though.
I did a lot of looking around online, trying to find a formula that people used consistently to raise baby rabbits successfully. What I found was a formula that worked okay sometimes, and fresh goat's milk that worked okay sometimes.... but a lot of people who tried them (especially the formula) did not have good results. Hungry bunnies, wrinkly tummies, etc. I had read on here where someone talked about how nutrient-dense rabbit milk must be. It hit me that the formula they were using (which had you adding water) might be too weak.
The starting formula was: 1 cup canned goat's milk (which is double strength), 1 cup water, 1 tablespoon corn syrup, and 1 egg yolk. I decided to nix the water... and then I made only half a recipe, because I was feeding only two bunnies at the time. It's hard to halve an egg yolk, so I just used the whole thing. New formula: 1/2 cup canned goat's milk, 1/2 tablespoon corn syrup, 1 egg yolk. Once the bunnies got used to the eyedropper, they loved the formula, and grew normally.
Okay, I don't know why I'm talking so much. I'm sick. :doc:
Here are a couple of threads on mastitis:
post241613.html
post242219.html
If you get antibiotics at the feed store, you will probably need syringes and needles, too. Get the smallest ones they have, at least 5 of them. Someone cautioned against straight penicillin, but Penicillin G Procaine (Pen G) is what you usually find at a feed store. Get a probiotic, too. Come back here for help on dosage and administration. If you can't give your rabbit shots, you'll need to take her to a vet. Or put her down.