Scope community team
Scope have put your post in the 'ask a benefits advisor' group, but I'm afraid this is not within the remit of benefits specialists, what you need is a Community Care specialist, of which there are many across the UK who would be glad to have a look at this for you.
From my scanty knowledge of the area, I do not believe that there is a strict 'national criteria' I believe that it is based on the needs assessment the Local Authority make, which should be holistic. It is indeed not the norm however for Direct Payments to be paid to partners, so this may be where you come unstuck.
CAB have some information on their website https://www.citizensadvice.org.uk/wales/family/looking-after-people/direct-payments-w/
I would recommend getting this checked out by a Community Care specialist. If you go to 'find a legal adviser' and search by specialist are in Community Care it should show ones local to you https://www.gov.uk/find-a-legal-adviser or if not, try your local CAB or law centre.
Hope this helps.