I wonder if one of the care home staff or even the manager could have a word with your dad. Get them to tell him that they are only there to support both of them with the physical side of mum's needs but that they can never replace the role that he has as her carer. Point out to him that they need his help. He knows her likes and dislikes. He is very important because he makes her happy. Whilst the staff can do the physical burden of caring they don't have the time to do anything else. This is where he comes in. They could tell him that she is fine early mornings whilst they get her up and washed and dressed but from, say 11am onwards she would like his company. He could 'take over her care' at that time and have lunch and evening meal there...saves him cooking at home and shopping and the meals are not expensive, he just needs or you need to book him in.
So, what are they going to do when he's there? What was their life like at home? What did they enjoy doing? On a day to day basis he could help her sort out her clothes. Make sure everything is back from the laundry and check if new labels are needed. What about things like her favourite toiletries? What else does she need for her room? An ornament from home? Pretty box of tissues? Photo album? Maybe they could sort out all their old photographs and put them in a nice album? Does he know where their address book is at home? Now's the time to sit down and write those Christmas Cards. Maybe you could print off a note that includes mum's address at the care home and let people know she would love to hear from them. Talking of Christmas, he needs to think of 'their' room. Maybe take him shopping for a small Christmas Tree, some of those sparkly battery operated LED lights would look nice too. Have they got a CD player in the room? Only ask because Christmas Carols can be one of THE things that folks respond to and often can sing along quite merrily. Hairdresser! He needs to organise this as sometimes the staff forget. He also needs to check what activities are going on in the home and put their names down if is something they like to do or maybe it is something new they'd like to try.
You could also help your dad by introducing him to other relatives etc. as they will often be feeling the same as him. With your help this could become an extended family for them both and somewhere that they can continue their lives together rather than feeling that things have ended.
With all these things for him to do, he's going to be a busy man. All he is leaving for is to get some sleep, have a bath, change of clothes and off again. So, not much different to how it was before but minus the stress of cooking and cleaning and bathing AND all the things that took up the time they could be spending with each other. Your mum is in a new HOME, not a prison. This is important for your dad to understand.
Fiona