I don't know what's next for my father, and we are both stressed out. Any guidance?

I wrote one question on this site years ago, but at that time I wasn't sure whether my father was also connected to this site, and in case he was, I wanted to make sure that he didn't notice my question, so I reversed my parents' genders when I asked the question. I'm pretty sure I'm "in the clear" now, so although my original question mentioned that my father had dementia, it was actually my mother who had it. My mother died six months ago, and my father is now living on his own. I'm in the same city (I moved here because of my mother's illness), and we have no other relatives in North America other than my sister who lives on the other side of the country. Neither my father nor I have much of a social network here - he and my mother moved here a couple of years before I did, and my mother was already ill by that point, so it was pretty difficult for them to find friends (although they did find a few). And I'm just a person who likes to be alone most of the time (also my work keeps me very busy).

Okay, that's the backdrop. Current situation: my father is becoming very stressed out. His memory is now extremely bad (i.e. he will repeat the same questions several times in one short conversation, and then again in the next conversation, and so on), and he is in the habit of writing down everything that he is thinking, in an attempt to make sense of things. This is helpful in a way, but he writes himself little messages in various different places in his home and it is becoming confusing even for me. To add to the stress, he nearly became the victim of a phone scam two weeks ago (and not even a very sophisticated one). I was able to intervene and no money was lost, but it's clear to me that something like this could happen again. Precautions that I have taken include telling him many times not to answer the phone unless he knows who is calling (but he sometimes still does pick up the phone for unknown numbers - I know this because I check his cell phone); taping the words "don't answer unless you know the caller" to his cell phone and his landline phone; and recently I set his cell phone to "do not disturb" (the phone only rings if people on his "favourites" list are calling). The unintended consequence of this is now he worries constantly about everything, and I think he is quite overwhelmed. I think it must be very frightening to go through life with no memory of anything that has happened recently, no ability to follow a set of instructions, and virtually no understanding of numbers. On the other hand, he can cook his own meals, drive to familiar places (although he drives less and less now), and his home is always tidy (not extremely clean, maybe, but never messy).

I have POA but I'm not sure that that's a very good thing since I don't have a lot of knowledge about the financial world and I really don't have the time or brain power to deal with two people's finances (his and mine). I know that when the time comes that he can no longer look after himself, he will need professional care because I am just not up to the task of caregiving (I am in awe of people who can do that, but after going through that hell with my mother, there is just no way). But I don't know how far we are from being at that point - and that is a situation that I am dreading, a lot.

Honestly, I don't even know exactly what my question is at this point, but if anyone can look through what I've just written and offer any kind of guidance, I would be very grateful. My stomach is in knots.