I agree about starting with the takeaways. Perhaps you could buy the supermarket equivalent routinely as part of your shop and have those instead of the takeaways, which is likely to be a big money saver.
Are there easy meals that you'll always feel able to cook? Omelettes, beans/egg on toast?
If you're likely to shop daily and buy takeaways, even when you've been to the supermarket for a 'proper' shop, perhaps it's time to not bother with the proper shop and just do the daily shops then try to cut down to every other day, by thinking 'what do we need for today and tomorrow' and then perhaps twice a week later on, a gradual process? Do you have a lot in, or waste a lot of food that goes off?
Or could you use Gousto, Hello Fresh etc, but focus on the quick and easy meals - many of the normal ones are quite involved cooking, so might be too challenging.
It's hard to advise, because I have lots of suggestions, but recognise the challenges you face, in terms of what you will be able to do.
If you say you are comfortable with money, can you afford help? Almost like employ a 'personal assistant' who does anything you need? Organising bills, hand hold while decluttering, cleaning, organising your fridge, helping with meal planning, whatever you need. Or can you ask a trusted friend or family to help you?
You could look at the advice on Moneysaving Expert for help with budgeting, but I'm not sure if that's something you have the headspace for? They do an online course too, which may or may not help?
www.moneysavingexpert.com/family/money-help/
On the smoking, is it Champix or similar that you're on? DP had those and they worked, but I think it did knock his mental health at the time, but he did manage to stop smoking and it was the only thing that worked for him after multiple attempts to stop over many years.