Ask an Immigration Solicitor. Get an Answer ASAP.
Unfortunately, if you are not able to sponsor and support your dad in the UK, he isn't able to join you as an adult dependent relative in the UK.
You need to show you are able to support your dad with his care in the UK without claiming benefits.
EEA nationals have rights to reside in the UK. Your mum will not be able to claim benefits until she meets the habitual residence test.
Please rate to receive any further answers
Sorry I cannot support you further without a rating.