Caring for Dad with tongue cancer

Hi, my dad was diagnosed with tongue cancer 2 years ago, he has had radiotherapy, 2 lots of chemo and 2 ops but the tumour has gradually got bigger. He has been told he can no longer have any of the above treatments as he is now too week. However, they have now offered him immunology treatment. Reading up on this it seems similar to chemo and I don’t know if it’s the right thing for him to do. My dad has given his consent but I’m not sure that’s what he really wants or if he’s going along with it for my mum? He does have great difficulty communicating as his speech is very limited due to the growth and at times he seems very confused. He spends the majority of the day (and night) in bed and doesn’t ever have the tv or the radio playing. He hasn’t been able to eat properly for almost 2 years and in the last year he now always feeds through a PEG tube in his stomach. My dad refuses to take most medication (even paracetamol) as he say it makes him feel worse, which means helping him with the symptoms is almost impossible. My question is what do we do now? Is it right to go ahead with this immunology treatment? Is there more help out there for my dad and us as carers? The palliative care Dad is currently receiving isn’t great as they only come in once a week, if we’re lucky and also because my dad can communicate to a certain degree then if he says he doesn’t want something then that goes and nothing else is done to help. It’s almost like we are just waiting for the inevitable to happen. It’s just a living hell.