My husband has denied the need for a POA. After 3 years, he still denies his dementia diagnosis. Now, sometimes he does not recognize me. Any advice?

You cannot get POA. POA is a voluntary action done by the person who must be competent and of sound mind. It is too late for that. You will have no trouble getting guardianship over your husband. See an elder care attorney to do so and take the letters of two examining MDs that your husband is no longer competent to make his own decisions, and giving his diagnosis. You can do this more easily if he is ever hospitalized as a Social Worker can often get you emergency temporary guardianship, which easily can go to full guardianship.
You might first of all check any wills that you and husband did in past. They often have documents called "springing POA" or DPOA (durable POA) that take place when needed with the presentation of the two documents from MD. You will still need those and the attorney. So basically make an appt with an attorney and take what wills and documents you have.
If you have nothing, the step #1 is to get a diagnosis that your husband is no longer competent and needs a guardian.

You husband is already mentally incompetent. His signature is worthless. You have to contact an attorney who will take him to Court. The Judge after verifying that your husband is incompetent, he will appoint you as his legal guardian and also your back up.

Go talk to a Certified Elder Care Attorney for guidance with POA and placing him. I placed my mom in Memory Care and there was no need to show my POA at all, but then again, she wasn't fighting me about being placed either.

Your DH isn't recognizing you or your home b/c he's regressed back in time to when he was 30 years old (or younger) and you weren't married or living in the home you're in now, so you and the house do not feel familiar to him. Paranoia about money & 'stealing' goes with the territory too, unfortunately, as the disease progresses. In home care gets harder and harder, too, as the progression continues and the decline furthers. Don't put yourself in harms way to keep him at home TOO long, and risk injury by doing so. A person with AD/dementia doesn't realize their anger and rage can hurt someone they love; brain disease has a way of doing that to a person, sadly. Stay safe, is my point.

Here's a great article to download:
Understanding the Dementia Experience, by Jennifer Ghent-Fuller 
https://www.smashwords.com/books/view/210580

Here is a list of useful tips from her e-book I found to be excellent:

The “Dont's”
· Do not reason and argue
· Do not demand that they reason or problem-solve
· Do not demand that they remember
· Do not demand that they get their facts straight
· Do not correct their ideas or scold them
· Do not reorient them
· Do not think that they are being uncooperative on purpose
· Do not think that they really do remember, but are pretending not to
· Do not use a “bossy” dictatorial attitude in care
· Do not act with impatience
The Do's
· Enter into their frame of reality, or their 'world'
· Be aware of their mood or state of mind
· Use few words and simple phrases
· OR use no words, just friendly gestures and simple motions
· Do everything slowly
· Approach from the front
· Wait for a slow response
· Constantly reassure them that everything is 'OK'
· Keep people with dementia comfortable 'in the moment' - every moment
· Maximize use of remaining abilities
· Limit TV or radio programs which they may feel are frighteningly real
· Maintain privacy
· Provide a safe physical environment
Language Needs
· Use short words
· Use clear and simple sentences
· Speak slowly and calmly
· Questions should ask for a “yes” or “no” answer
· Talk about one thing at a time
· Talk about concrete things; not abstract ideas
· Use common phrases
· Always say what you are doing
· If they repeat their question, repeat your answer as you did the first time · Give them a longer time to process information
· Wait patiently for a response
· Be accepting of inappropriate answers and nonsense words
· Speak softly, soothingly and gently

Care Needs
· Recognize that receiving personal care feels intrusive
· Reassure with your tone and manner
· Do one thing at a time
· Talk through the care “play-by- play”
· Be aware of your body language and use it to communicate relaxation and reassurance
· Be sincere
· Use a soft, soothing touch
· Be aware of the individual’s unique triggers
· Be aware that a person with dementia may not accurately judge whether a situation is threatening to them
· They may respond to fear, pain or anxiety by defending themselves with what we call “aggression”
· If they become distressed, stop immediately and allow them time to calm down – don’t try to restart the activity right away
You need to change your behaviour to adapt to the dementia because the person with the disease cannot.

Another good book is Living in the Labyrinth: A Personal Journey Through the Maze of Alzheimer's, by Diana Friel McGowin. Learn all you can about AD/dementia b/c knowledge is power!

Wishing you the best of luck with all you have on your plate.