Carers Allowance & Univeral Credit

He can't claim ESA because he's claiming UC. He can claim for the limited capability for work but for this he'll need a sick note from his GP. The process of that is similar to ESA and eventually a face to face assessment is most likely. Evidence will also be needed to support his claim.

PIP isn't about a diagnosis, it's how those conditions affect your ability to carry out daily activities based on the PIP descriptors.

Being your carer could well go against him for both of those claims but it will depend what help he gives you and the reasons for the PIP/LCW claim.