hello
@Jrwels
a warm welcome from me too
you say your mum has early onset dementia, so maybe she has a diagnosis ... if not, the suggestions already offered may help ... let your dad know that stress, delression even vitamin deficiency can present with similar symptoms and so it's worth having a check up in case any of these are 'at play' and can be treated ... her GP may choose not to discuss your mum's health but has to note any information given to them, so it's an idea to write to them with details, and keep writing with updates, so they have a full picture to help with diagnosis ... your dad could make an appointment bjt tell your mum it's for him but he'd like her to go with him for moral support
if there is a diagnosis, you may mean that your dad is reluctant to arrange an assessment of your mum's care needs by their Local Authority Adult Services .. often people don't want to bother anyone or feel they have to cope themselves 'as that's what marriage is about' ... maybe let him know your mum has a right to this assessment, as he does to a carer's assessment ... and that no-one will try to part them as it's very much the principle now to support people to stay in their own home, with home care visits (to take some of the strain of physical tasks), day care (so they each get a break, time for themselves), respite (a week away for your mum means she is well looked after and your dad catches up on his rest) and OT visits to suggest aids and adaptions that can help and may even be paid for by the LA or provided more cheaply than organising them himself ... indeed, the sooner he gets support in place, the more likely he is to be able to look after your mum at home for longer ... it's no reflection on how much he loves his wife that he is sensible enough to see no-one can care for another adult alone, we all need help at times
https://www.alzheimers.org.uk/get-support/legal-financial/assessment-care-support-england
he may be worried about finances .. this may help you put his mind at rest
https://www.alzheimers.org.uk/get-support/legal-financial/who-pays-care
he may fear he has to sell their home, and this is definitely not the case ... it is disregarded in any financial assessment for your mum's care as long as he lives there
maybe look into Attendance Allowance for your mum, depending on the level of her needs ... it is a benefit awarded solely on need, it is not means tested, so is well worth applying for ... or PIP if your mum is below 65 ... after all, they have paid into the system, so deserve some small benefit to help them
by the way, it will help you to support them if LPAs are in place for both of them, so help your dad look into arranging these
https://www.gov.uk/lasting-power-attorney-duties
sorry if none of this answers your post