There might be quite a lot you can claim financially and also quite a bit of help.
First do the PIP form and ESA as well, anyone can fill these in, get an advocate if you can to do it. I used to fill in lots for people and it doesn't take long once you are used to the forms, and do it from the perspective of a 'bad day' if he has good and bad days.
Carer's allowance is a possibility but slightly more complicated and sometimes it takes thinking about whether you would be best to claim it or if there is another family member who would be better given there are earnings limits and hours constraints on it.
Basically it's as follows, as it's considered a 'wage replacement benefit' which tbh is dreadful :-
You must look after someone who gets a qualifying disability benefit
for at least 35 hours a week, you must not be in full-time education
you can't earn over £120 a week (after deductions).
The qualifying disability benefits are Disability Living Allowance (where that still exists- higher or middle rate only), Personal Independence Payment (Daily Living component), Attendance Allowance and Armed Forces Independent Payment.
The £120 per week ceiling for claiming Carer's allowance is particularly harsh and they are quite stringent about how they enforce it, however if you are in employment and are paid monthly, your monthly earnings are normally multiplied by 12 months to get a yearly figure and then divided by 52 weeks to get a weekly figure.
If you are in employment and have fluctuating earnings it is possible for your earnings to be averaged out over a recognisable cycle of work or over five weeks.
If you are in self-employment your average weekly earnings are normally calculated by looking at a specific trading period, which is normally a year. However if you have only recently started your self-employment, or if there has been a change in your circumstances, then a different period more representative of your average weekly earnings can sometimes be used.
The following amounts are deducted from your gross weekly earnings (if you are in employment) or your net profit (if you are in self-employment) before your earnings are taken into account for Carer’s Allowance:
Income Tax
National Insurance
half of your contributions towards an occupational/personal pension
If you already claim an overlap benefit you are also not entitled to carer;s allowance AT ALL ( which is frankly a disgrace as it means a slightly less disabled partner cannot be a paid carer for their partner or indeed a pensioner).
State Pension
Contributory Employment and Support Allowance
Incapacity Benefit
Maternity Allowance
Bereavement or widow’s benefits
Severe Disablement Allowance
Contribution-based Jobseeker’s Allowance
If I can help any further let me know but I would also contact various Kidney charities as discussed and speak to the carer's support service for advice on getting in help as well. x