Aged parents

dragonfly46 No suggestions really just a big hug and lots of understanding about what you are going through. It is hard deciding what happens to a parent. Is your dad capable of understanding what will happen to your mum and of giving his own opinion? Perhaps he may decide to say 'goodbye' to her realising she will not know him. On the other hand if he can be taken for a visit occasionally he may be happier.
This may sound dreadful but I would encourage anyone with older parents, particularly if they are in hospital to discuss a Do Not Resuscitate notice with them. It was something we did for my mum and I am so thankful, it enabled her to go peacefully.

Are the different units adjacent to each other? If so, could you agree with staff that Dad is wheeled through for regular 'visits'. or perhaps you could do this when you are visiting?

Sadly, as dementia progresses the memory that should prompt recognition of loved ones, is lost. You say your Mum is quite happy in her own world. It might be kindest to leave her there, unless your Dad is pining for her. Very hard on you but take comfort that soon they will be together for eternity.

They are suggesting a move, but actually they can't keep her in her current situation if it becoming unsafe. They are responsible for her care and well-being. I think the decision has, in effect, been made for you.

Can you take your dad for visits, just like you will visit. Or arrange for an extra carer to facilitate visits to your mum. They could use a wheelchair. Just as any relative would if their partner was in hospital say.

His health may also improve if he doesn't have to feel a degree of responsibility for what your mum is doing.

It's very, very hard, I know ?

Is the dementia unit on the same site, could you or a member of staff take your father to visit your mum sometimes, or could your father also move with her, ?
It would be sad to part them because even if your mum doesn’t know him, he knows her.
I have experience of how hard this so do understand and hope something can be sorted out.