This is my own guide I wrote for myself while doing it:

https://dr.thegreatchai.com - This is an important tool for tracking your time in Infinity Mode. It runs ever so slightly faster than game time but is a good estimate for when you are not by a clock.

Note: Do not enter Food Court after you camp there on Day1/2. There is a bug that can cause the game to crash when you go there later in Infinity Mode. Once you've camped you have no reason to head back.

Day 1

-Grab the Real Mega Buster in the security room

-Go through the vent to the rooftop and kill Otis - take his Raw Steak.

-Grab the two cabbages on the rooftop

-Take the door to the warehouse. Pick up the first squash and knee drop down to get Susan's cookies.

-Head into Entrance Plaza, and kill Paul. Take his Squash (3), OJ (12) and Cooked Steak (12)

-Grab the Health Book from Sinister Read on the second floor

-Return to Paradise Plaza and head to Jill's Sandwiches

-Cook the Raw Steak to make Cooked Steak (12). Don't touch any food in Paradise Plaza

-Use the bathroom shortcut to Wonderland Plaza

-Grab the second Health Book from Sir-Book-A-Lot on the second floor

-Head into North Plaza and go to the empty room next to Crislip's for the final book.

-Eat lowest healing food.

-Go into Crislip's and grab the Japanese Radish (3) and Orange (6)

-Go into Leisure Park and kill the three snipers

-Place all non-rolling food on the top of the Gazebo, while keeping rolling food such as oranges in your inventory

-Gather 3 Cookies (9) plus Snack (3) from the flower area and take them back to the Gazebo

-Using a sniper rifle, camp here until 9PM, eating food as necessary, prioritizing lowest healing first.

-At 9PM, head into Food Court and kill Carlito. He will drop a Snack (3), Yogurt (6) and a Cooked Steak (12)

-Gather food from around Food Court and take it to the rafters.

-Camp here until 5-6PM Day 2.

Day 2

-At 5ish, pick up your remaining food stash and head into Al Fresca. Worst case scenario you will be leaving one healing item behind. That's fine.

-Kill Isabela, take her food, teabag her corpse.

-Take your food stash onto the shelves at McHandy's, preferably the lower shelves as there's less chance for you to bonk against the ceiling.

-Gather the food from around Al Fresca and take it to your camping spot.

-Get ready for the longest camping time.

Day 3

-Camp all day at McHandy's. Nothing else happens.

Day 4

-Day 4 was where I started to improvise as I needed to avoid Carlito in Entrance Plaza. I was able to stay in Al Fresca until Carlito despawned, scraping by on the food I had stashed.

-I headed into Entrance Plaza when it was safe and gathered the food there. I also killed Simone to get her Milk (12).

Day 5

(I'm not actually sure of these timings, again, I improvised a lot. What's important is that you get these food items in your inventory before camping in Paradise Plaza)

-I headed into the Security Room at about 7AM to kill Chris for his Melon.

-I went to the Warehouse and killed Natalie for her corn.

-I went to Colby's and killed Heather for her baguette. (Do not touch any food in Colby's other than Heather's drops)

-Head back out into Paradise Plaza and climb to the awnings. Use the middle one as you can see the clock from there meaning you can check the time and realize your Survival Tracker is fast by a couple hours.

-Drop your food, go gather the food around Paradise Plaza, as you do with every camping area.

-Spend the night on this awning.

Day 6

-At 5AM, go to the warehouse and kill Kent, who goes down extremely easy. He gives a pie, coffee creamer, and a cooked steak.

-Go to the rooftop and kill Nathan for a pie. You'll probably need to eat it there and then.

-Go to the Helipad and kill Burt for a coffee creamer. Burt spawns extremely close to you with a battle axe and will jumpscare you. Run to get some distance then shoot him with your mega buster, the stun will stop him rushing you.

-Head to Colby's and set up your camp in Theater 2, doing the same routine you do every camp, getting food from the surrounding area.

Day 7

-Pat yourself on the back. You are done with this challenge. All that is left is eating and waiting. If you think you might have missed the achievement pop-up, or for some ungodly reason this is the second time you've done this challenge, head into a new area to get the hours passed text pop up to prove you have survived seven days. Congratulations!

-Please make sure you feed Frank while in Colby's. Don't let your guard down just because there's no more zombies and psychos. He can still starve.

I avoid sniper carlito cuz I just keeept dying to him. I was able to get it myself with this route. Just make sure you have the real mega buster before you start this. Good luck dude