Thanks for your question
I am sorry to hear of the struggle your brother has been facing.
As he is still officially employed by his employer then I am afraid that most benefits will not be due for claiming, however, there might be scope for a claim for Disability Living Allowance, although this will be dependent on how much care your brother still needs, either with personal care, or mobility.
But I have added a link here
This gives a more in depth detail, as to the eligibility considerations, along with rates payable, and how to make a claim, and this is not means tested (so his savings will have no detrimental affect on any valid claim)
But I am afraid housing benefit, council tax (other than single adults discount which might apply if he lives alone) employment and support allowance, are not going to produce a valid claim, all the time his savings are in excess of £12,000 and savings between £8000 and £12,000 see a reduced claim.
As far as tax refunds are concerned, the employer would have considered this each payroll run, when paying the £90 sickness benefit, and you may find that some tax is being repaid from deductions made since April 2013 to the date of the last full pay. So do ask the employer, if you are unable to establish whether this is the case from your brothers payslips.
I am sorry the news is not more favourable.
Do feel free to ask any follow up questions.