PIP and LCWRA are not linked for existing claimants.
Even if the changes go through, if you're already in receipt of LCWRA, you'll continue to receive it. LCWRA isn't dependent on receiving PIP and any changes are only being applied to new claimants. Even if you are re-assessed and no longer qualify for PIP, you won't lose LCWRA as it's different criteria for existing claimants.
So hopefully that means things won't be as bad as you fear.
Secondly, you really do need to get a handle on your eating.
I am autistic/ADHD and am fucking terrible with getting things done. I live with three disabled people, and someone else who's on long-term sick as they collapsed with a neurological condition which isn't improving. Believe me when I say I understand the challenges of disability and the impact it has on your life.
You need to change your patterns of thinking. You stopped at a garage to buy a can of coke - you could have picked up something there for lunch at the same time that's healthier than a pot noodle. There are plenty of semi-decent options at garages. Also, coke isn't going to help you. You'd have been better off picking up fruit juice - that has natural sugars to give you energy without all the shite, and it would contain some nutrients.
You say your DD's food is sorted every week without any issues. You need to figure out what changes you can make to keep some healthy food indoors for you too. Completely understand that you don't want food that's going to go off if not used, but a PP gave you some brilliant examples of grazing food that would be better and would last - nuts, healthy snack bars, quick oats for porridge, frozen fruit etc. If you can make a pot noodle or chuck a pizza in the oven, you can manage all of these and your body would be better off.
When you struggle, you need to do what you can. Take the little wins. Manage the little things. It doesn't sound as if you're doing that. You're probably exhausted from managing your condition but it's a vicious circle. The worse you treat your body, the worse you will feel. Eating better won't magically heal you but it will help you cope. Everyone feels lethargic and achy on a diet full of shit. When you have a condition like CFS, this will be amplified a million times over. If you have a sugary/high caffeine drink like coke, when the inevitable blood sugar crash happens, anyone would feel like they could do with a nap, but more so you.
I'm not unsympathetic at all. I'm absolutely furious with Labour and feel so very let down. I'm terrified about what the future will hold for my disabled DC.
And worst of all, no one really cares. The country is in such a state that everyone just wants things to be better, and they believe the hype around lazy claimants and made-up disabilities.
But that's exactly why we need to be doing the best we can. I understand some things just aren't going to be possible for you, but there are small changes you could make that would make an infinite difference. Figure out what changes you could make and determine to make one small change each week. For example, this week get registered with Lloyds online pharmacy - it takes five minutes and you don't even need to ring your GP to re-order your prescription. Maybe next week, add five items to a list of favourites at an online shop. Over the next few weeks, add five more items each week until you have a basic shop saved. Then whenever you need to shop but don't have the energy to put together a full online order, you only have to make about four clicks online and a delivery will be on its way. No distraction, no reason not to have healthy food at home for you.
Take it as slow as you need to but make a plan for yourself. It's easy to feel hopeless when there's no end in sight. But no one is going to look after you, so you need to look after yourself.
My mum has cerebral palsy so I was a young carer. She now lives with me as an adult. Living with a disability is exhausting, unfair, and just shit all round. It's really easy to stop making the small changes that are possible because it all seems like too much.
Do you have antidepressants? If not, do you need them? If you do take antidepressants, does the dose need to be increased? Conditions like CFS can take a real toll on your mental health. Taking antidepressants doesn't mean it's all in your mind - CFS is real but the ongoing exhaustion often leads to co-existing anxiety/depression etc which can make everything feel even more of an uphill battle.
The written word doesn't always translate terribly well, so please take this with the kindness it's intended. Nothing is going to make you feel magically all better, but giving your body the best chance to keep on slogging through really is important.