It will help for you and your mother to realize that one person, even one person with in-home assistance, cannot possibly meet all the physical, emotional, mental stimulation, and social
needs of a person with dementia. What tends to happen is that as the healthier spouse tries to keep the other at home, his physical needs get met first but the other needs are neglected.
You may have seen statistics that show that the well spouse is at very high risk to die before the ill spouse. This is because the needs of the well spouse are neglected because they are exhausted from caring for the ill one. This also leaves the ill spouse at home alone without his primary caregiver, and he will have to be placed in a care facility.
A much better solution for EVERYONE is to allow others to meet your father's physical needs in a care facility, then have your mother visit to provide emotional support, arrange for mentally stimulating activities, and engage him in social activities.
As part of my care manager responsibilities, I recently moved a husband into a nursing home while his wife remains in assisted living. I arranged a driver to take her to visit her husband daily. It has been surprising to notice that a 2-hour visit is really all either of them wants.
I have made similar arrangements for other couples, and the results are much more satisfactory than having the ill spouse remain at home. The well spouse can continue to have meaningful activities without her spouse being dependent on her 24/7. She can take time to have satisfying visits with him, and time to make sure that his physical needs are being met by the staff at the facility.
Look around at care facilities. Many have multi-levels of care. It's possible that your parents could move into the same community but not share a room. Remember that most married people do not spend 24 hrs a day with each other. They have brief mornings and several hours in the evenings, and do not consider themselves separated.
Your goal is always to make the best arrangements for both of your parents. Let your father and mother have separate space with lots of quality visits.