Hi maggie
As a mixed aged couple, benefits are now based on the age of the youngest in a couple.
I would advise you to seek help from a Welfare Rights Organisation who can take all your circumstances into consideration; You can find your local Welfare Rights Organisation to help you with advice by clicking on the link below and putting in your post code, it will then come up with a MAP with a list of agencies.
advicelocal.uk The reason why he was asked to send in a 'fit note' his work coach will send him a work capability assessment (WCA), if he passes the WCA the he will be placed in the LCWRA group (Support) and will receive an extra premium with his UC.
Gary