Hi - I think the key question here may be not whether he wants to grant you PoA or not, but just how 'muddled' he has become.
The solicitor will want to establish he is still compos mentis enough to make the informed decision to grant you PoA - I'm pretty sure that if the solicitor is doubtful about his mental capacity he won't be able to process anything, even if your father wants to do so. In my (very limited!) experience the solicitor will deliberately ask your father open ended questions that can't be answered 'yes' or 'no' too, and which you won't be allowed to steer eg, by prompting 'isn't it, Dad?' etc.
He'll be asked open questions such as 'how many children do you have' and 'what are their names' etc, hopefully within the context of the general topic of PoA, so perhaps your dad won't 'twig' that he's being mentally assessed by the questions!
If the solicitor has doubts, he will have to refer the matter to your dad's GP and possibly have a mental capacity test. And if your dad fails that test, then he can't grant PoA to you. Indeed, you may then be legally required (???) to go to the Court of Protection (I think that's it!) to entitle you to 'take over' your dad's finances. BUT, the downside of that, I suspect, is that then YOU become 'legally responsible' for your father's finances AND his general well being (ie, as if he were your child) ! That responsibility may not be something you actually want.
For myself, it's not aquestion I want asked at all right now of my MIL - I don't want the issue 'put to the test' before it absolutely HAS to be done! Instead, what we've done is to open a joint bank account (her and me) so I can sign cheques for her spending her money. It's not ideal by any means as half the fund then legally 'belongs' to me (and if I peg out before she does - and some days I truly think that wll happen, and she will see us all out! - that may impact inheritance tax etc etc.)
Others may know more, but there may possibly be a half way house whereby the money stays in your father's account, but he gives the bank permission for you to withdraw it for his own needs, or sign cheques (but not formal PoA).
To my mind, the whole issue is a minefield! There's the problem of the implications of being judged not to have mental capacity any more, plus the problem of the caree knowing that (which may be a bit traumatic for them!), plus the problem of them not knowing that they have reached the stage whereby they should grant PoA, or, indeed, not knowing they have reached the stage of not having legal capacity at all!!!! (Hard to tell someone they are mentally 'gone'......)
Hope others here may clarify, and perhaps give you a more optimistic reply.