So, based on what you described so far, really the hardest part is about storage and refrigeration. But there are some items and tactics that might help.

The one consistent thing you have is your car, so setting up a dedicated area in your car for transporting your cooking and storage materials is crucial. I also think you need to break down your meal prep from one day a week to a few (I'll get into that in a moment) and rely on fresh, quick grocery runs when possible.

Here are a few of my favorite easy prep ideas:

1. Steam veggies in frozen bag - buy the smaller ones and eat the whole thing, or get fresh veggies and steam in a reusable steamer container: https://smile.amazon.com/Sistema-Microwave-Collection-Steamer-Large/dp/B005D6XZ4O/ref=pd_bxgy_2/133-3482367-5870229?_encoding=UTF8&pd_rd_i=B005D6XZ4O&pd_rd_r=065e1af9-015e-4991-a2a3-e924c19ac2c9&pd_rd_w=eJM4r&pd_rd_wg=EglHS&pf_rd_p=fd3ebcd0-c1a2-44cf-aba2-bbf4810b3732&pf_rd_r=5MNHXQ9RRZHMBRPK66DV&psc=1&refRID=5MNHXQ9RRZHMBRPK66DV
2. VeeTee pre-cooked rice - I've tried every pre-cooked rice available, and these are by far the best. I ship them to me via amazon, and one container is exactly two servings. https://smile.amazon.com/stores/Veetee+Rice/page/44245AA2-25E1-436D-97EC-E18273606922?ref_=ast_bln
3. Potatoes - Potatoes can be great, especially once you learn how to microwave one into a baked potato. I'll also argue here, Wendys has a really decent plain baked potato. https://smile.amazon.com/OBTANIM-Microwave-Potato-Reusable-Cooker/dp/B07QR2T2MX/ref=sr_1_5?dchild=1&keywords=baked+potato+microwave+cooker&qid=1621611223&sr=8-5
4. Pre-packaged foods - I know everyone will tell you to stay away from them - too many extra artificial ingredients, to much sodium, etc. But you are honestly not in a position to brew up your own chicken stock to then make a homemade chicken noodle soup. Look at the labels, Look at your macros, including sodium, and make choices that blend your need for healthy and your limitations on what you can and can't do. I always use canned soup (except for my chili, down below) and a lean cuisine is a decent choice for very low calorie food. I look for low sodium items if possible. Take a good look around your grocery store for individual sized portion control items. Think everything, from individual olive cups to pickle chips, to mac & cheese. Yes, you're spending more for the individual sizing, but they are made for people like you.
5. Chicken - at least at first, try the pre-grilled chicken packets as they are resealable and can keep pretty cold (don't buy on amazon - they're at all the grocery stores, but I'm including the link so you see what they look like) https://smile.amazon.com/Perdue-Carved-Chicken-Breast-Grilled/dp/B06XC1WHYK/ref=sr_1_2_0o_fs?dchild=1&keywords=perdue+chicken+strips&qid=1621607683&sr=8-2
6. Sauces - for me chicken requires some sort of extra flavor, so I like to use a few low calorie dressings ore sauces to amp up a meal. Downside is that they require refrigeration. I always keep an italian dressing, low fat sour cream, a Thai peanut sauce and a Tzatziki in my fridge, and with a good size cooler, you can keep them relatively refrigerated. You may also consider putting them in smaller travel containers like these (I use Sistema, but there are plenty of good brands out there - I like that when I screw the lid on you can feel the click at the end to know its on tight) https://smile.amazon.com/Sistema-Collection-Bites-Storage-Containers/dp/B00Z9C4CT4/ref=sr_1_3?dchild=1&keywords=sauce+containers+sistema&qid=1621608980&sr=8-3 To protect these you might even put these containers in a large yeti or water jug for extra protection
7. I also recommend that you look at a restaurant supply store for individual portion control condiments, if you can't live without your mayo or frank's hot sauce: https://www.webstaurantstore.com/85/condiment-portion-control-packs.html
8. Make a point of leaving the office and routinely hitting up a grocery store - pick up just fresh or frozen fruit and vegetables for dinner, the next day's breakfast and/or lunch. Once it's routine for you, it won't feel like a heavy burden and you always get the freshest produce.
9. Chili - I make a chili with ten servings, and freeze most. This you can prep on the weekends, pack it up, freeze them, and use them to help keep the cooler chilled. I don't use expensive containers, but i do use locking screw top ones like this: https://smile.amazon.com/Ziploc-Twist-Container-Medium-Pack/dp/B010OVMETY?ref_=ast_sto_dp
10. If the hotels you stay at don't always include a fridge (or worse, fill it with stuff) If you have room in your backseat or trunk, I'd get a small dorm fridge like this: https://smile.amazon.com/dp/B01DZQI70K/ref=emc_b_5_i and a foldable trolley, and just wheel it in and wheel it out. https://smile.amazon.com/Aluminium-Folding-Lightweight-Foldable-Portable/dp/B01K1RUSU8/ref=sr_1_6?dchild=1&keywords=foldable+trolley&qid=1621610221&sr=8-6
11. Plate your food whenever you can - While I did not travel, I always kept two place settings at work in a box - two forks, two knives, two spoons, two soup bowls, two plates. Plating makes it feel like an actual meal and gives you an aesthetic balance that you might not realize you're missing.
12. I'd recommend this for anyone starting a food lifestyle change - what foods are you not willing to give up? Take those foods and build them into you routine. I LOVE cheeseburgers. LOVE hot sandwiches. So, rather than say no to them for the rest of my life, I build them into my calorie and macro counts. Don't say no to an item because it may seem "unhealthy" (well, say no to fried butter sticks, because there's no healthy to that at all, but otherwise there's usually wiggle-room)

This will seem like at first its taking over your life, and honestly, it will. You're literally packing up your car to feed yourself every week, and it will require daily and weekend prepwork to do it. But trust me, building this habit now will make you happier in the long run. Other than the refrigerator, everything I listed can be put into a solid size box and carried with you by car. I also recommend a solid wheeled cooler to keep in the car as well.