I totally agree with Sunkacola.
I know it feels like you can't find another job, you can't go into another field, but that is only a situation you are in now. You have to focus on the future and you first have to get used to the idea that you can do other things (other than 'food service') for a living. Research is key. Also getting to know yourself. What are you good at, what do you like to do, what kind of a job would be physically and mentally less straining on you?
For the last question, you have to think about the whole picture. I worked in office jobs my whole life, but I used to get so stressed out because I always felt people were watching me, so I worked nonstop, without taking breaks, typing typing typing, all tense and stressed out, no matter how much work I had done that day, I felt like it was never good enough....it finally gave me tendinitis and bursitis in my shoulders and chronic neck pain and head aches. Something so simple, yet when you overdo it, it ruins your life. Stress and the actions we take due to stress can ruin our bodies and minds.
So think about your stress levels. I am sure when your manager asks you to ''push on through' that it puts a lot of stress on you. How can you minimize that? Does it make you angry, want to cry at moments like that? what can you do to take yourself away from the situation and tell yourself 'My boss is a cruel man, who does not understand my situation. I might never be able to change him/her, but I can change the way I react to his negativeness'.
Is there anyone you can talk to about your frustrations? At work or at home? Or anyone in a supervisor role that you can communicate well with? Can you switch to hours that are maybe less stressful, where maybe less frying/lifting happens?
Did you look for ways to lift differently? In household chores, I myself have learned to do almost everything differently. Instead of taking one large trash out, I now have little trash bags that I bring outside throughout the day. When doing groceries, I make sure I either have my lovely shopping buggy with me (wheels - whoever invented them, thank you from me too!) or I only carry a maximum of 2 kilos/4 pounds in a bag that leans against my body. By spreading the weight of whatever you are carrying in larger area of your body, the strain becomes less. Thus also less painful. Next time you have to lift up something, think about other ways to lift it up. Can you maybe distribute the weight by opening up the box and taking some contents out? Can you maybe push it through the floor with your legs so you minimize the distance? are you lifting it up using your core muscles?
To avoid the bad smells getting to you, think about the smells that relax you. For me, I love the smell of soap. That clean smell. I finally found a body oil that I carry around in a little container. I also can't stand smells, and in the heat, where I live, people start to smell real bad (I know - disgusting!). I put that oil on my nostrils and close my eyes whenever I have to take public transportation. It takes me to another place and relaxes me. You can also relax by simply stepping outside and breathing in and out 10 times. This will also relax you, give you a time out.
And my last advice is to try your best to be physically fit and strong. Whenever you can, do strength exercises. You can do just 10 sit-ups every other day, and just standing up, you can engage your stomach muscles by contracting them. You can work on your leg muscles while sitting down. Look up videos online for basic, pain-free exercise options.
You are stronger than you think you are. It takes a lot of strength and integrity to be able to hold down a difficult job like yours. My total respect to you.