So I said above about checking for benefits i would check as on an income of £2500 month (does that include pip ?) With dc and two disabled you may be able to get something. Dh may need to apply for disability first but play around with the calculations.
On outgoings:
Mortgage £1200 - this is probably the biggest thing you can look at reducing. Not ideal but worst case scenario can you look at payment holiday etc (but try not to if your going to need a new mortgage which is harder on benefits but not impossible (I used barclays bank). I ended up selling my unsuitable 4 storey house and buying more suitable because my equity (not masses) meant I wasn't entitled to council housing but couldn't find disabled friendly rentals.
Council tax £211- if your entitled to benefits you may be entitled to a reduction (i also get a disability band reduction so may be worth looking /asking). Some local council have funds you can apply for too.
Energy £200 (I'm guessing if your already turning things off you need heating because both ill/at home all yhe time a smaller house would reduce this).
Car insurance for both £80 (do you need two cars?),
Phones x 4 £80 - this could be a big saving shop around get a sim only, I swap between smarty and leabara every year and presently got 3x sims 12gb for £16.20.
School dinners £200 (this is a big saving, make a packed lunch my dc has homemade pasta salad, cous cous or a sandwich with veg and fruit) all relatively cheap (compared to a school dinner).
Food £600 this could be reduced, go down brands, meal plan everything, dont allow constant snacking, I shop on line due to disability (and no longer able to drive) which stops impulse buying but also helps me plan. I also only shop every 10 days, have 2 extra cheap nights with either leftovers, jacket potato and beans or a something on toast night. I spend about £70 per 10 days for one adult and two older teens. Make as much from scratch as you can, I make a batch of soup for my lunch every day, we eat well but basic. I buy herbs and spices in bulk and so never one big outlay but always have something in. Lots of pasta and sauce, chilli, potatoes, frozen veg with something.
School bus and laptop rental £100 (can they walk? do your council have a free bus pass for low income families?) Can school help with the laptop rental (my dc get some support with the extras).
Fuel £100 - what is this for if your not working? Is there anyway to reduce it? Depending on your disability you may be able to get blue badge /disabled bus pass.
Water £40 - you may be entitled support, it depends on your water board. Mine have several schemes and I found that talking to them they could give me the best scheme for me. I pay a fixed amount of £33 a month.
You haven't said about broadband but so.e companies do reduced price for benefits (but not always cheaper), we're rural so limited but u have BT for £20 a month and it hasn't gone up for many years.
Not money saving but let the utilities companies know your disabled you can go on there priority list if theres ever a problem in your area and get priority service.
Another one is find out about young carers, get your dc registered in our area it isn't much just a short support course, they got hampers in lock down but more recently its meant getting on a university programme to support getting them into university which will hopefully be a big help. Both with a place at our local university so they can stay home and a a bursary.
The best thing to do is not stick your head in the sand, choose one thing and sort that and keep going till its easier. My life is always hard because of disability/minimal money but its been paid since I sorted and controlled what I could.