Hi Luke
I am still new to all of this, so I might not be suggesting the right thing, my husband was diagnosed with young onset Alzheimer's a week ago. We also started with a diagnosis of depression and anti-depressants, but as the anti-depressants did no good he was transferred to a memory specialist.
It might be worth keeping a diary of the symptoms/things you notice to share with the doctor. Does your dad let you attend the doctors appointment with him? My husband did not always explain all the symptoms he was experiencing as he was not aware of some of them. I attended appointments with him so I could explain them and also understand what the doctor was suggesting in terms of next steps, as my husband didn't always understand what tests were going to take place next. I could also explain how the ways he was behaving were out of character compared to how he was a year ago.
I have been worrying about the financial side too, there are lots of leaflets in here about benefits etc, plus if your dad is diagnosed with Alzheimer's or some form of dementia work would need to make reasonable adjustments to help him keep working if he is able to.
It is scary and being told that my husband had Alzheimer's was devastating but we needed to know and it means he now has medication which may help him (hopefully), he can ask for support at work and also I can understand why he is behaving as he is. I am still devastated but do now understand that my husband isn't being deliberately awkward.
I hope you get the help you need.