Rental income advice - Revenue worries

You say that " as he got sick some things went unpaid" and this included the life insurance policy.
However, many policies include a " terminal illness clause" . This will pay out if the client is diagnosed with a terminal illness, prior to death.
If your husband met the criteria, at the time he was paying for the policy, he may be entitled to a payment.
It would require a medical consultant indicating that, in his belief, the illness was terminal and likely to result in death.
It might be worth getting hold of a copy of the life insurance policy and lodging a retrospective claim.
 
If you can't find the paperwork see if you can find out the company from the bank statements and get in touch with them. It sounds like you are at capacity with your family, is there a trusted friend or relative who could help you? I can't imagine the stress for your family so if you can get help from someone you don't mind sharing your situation with it might reduce some of the stress.