I don’t have a super cool box, just a regular Coleman hard sided cool box. I cool it down the day before I go with ice for 24 hours. Then fill it with things that are properly cold already, and some things that are frozen to defrost (e.g. chicken for day 2, or a homemade meal).
I freeze proper large ice blocks - or a couple of 2 litre bottles filled 3/4 full with water (they melt a lot slower than ice cubes). A bag of ice is really helpful if you can get to a shop (even small shops now seem to sell bags of ice cubes) to replenish - or ask the site manager if there’s a freezer to refreeze blocks.
i also try to avoid opening the cool box as much as possible - so I use a picnic bag to take out everything I need for a meal at once and keep a little chill; or to put the bits that are used a lot like butter and the open pack of cheese etc.
I use a lot of eggs and cheese. Couscous with some veg stock powder/sundried tomatoes/olives added in only needs some boiling water to sit and be absorbed. Dried mushrooms are great to rehydrate for risotto etc. Chorizo is useful as another meat that doesn’t need hard refrigeration to join the bacon. A tin of tuna, a tin of corn, rice, onion, garlic, any other handy veg and some curry powder makes a lovely stir fried rice dish (nasi goreng). I recently found tortellini type pasta parcels with a ham filling that were dried rather than fresh in fridge - so they’ll need longer to cook but they’re on my cupboard shelf. Vegetarian chilli can be made using fresh and tinned veg (like carrots, onion, garlic, peppers, butternut squash or sweet potatoes, maybe courgette fresh- and corn and bean and tomatoes from tins) so can be a “later in the week” meal.
Also, while it mightn’t be your usual, are you so remote that there isn’t even a corner shop to get meat/fresh things a few days in, even if just for 1 meal? Splurge a tiny bit to get the wine that’s already chilled and some ice cream for dessert, throw those in when you get back to the tent and your cool box is chilled down again for another bit by the time dinner/dessert is done.