My husband has been scammed by sweepstakes pushers. They tell him that he has won millions but now needs to send a “service fee” to get the prize. Any advice?

If the money is gone there's not much you can do about it now. BUT for the future, read about online and telephone scams. These A-holes are getting more and more brave, I'm afraid.
Explain to your dad that it was a mistake. That a 'real' sweep steak does not charge for giving you money. This so sounds familiar, I think my mom went through something like this. There are call centers in Nigeria and Africa and God knows where else that phone people just to scam them.
Once he realizes he has been HAD, he'll be more careful. I hope.

Temper

He lost the right to have access to money and bill paying when he lost money to scammers. You are lucky it was only $500. Next time it could lots more. Take him off all bank accounts if you can. Take away checkbook and atm card and all credit cards. You need to protect yourself financially or he will destroy you.

And PCH. Have you personally had anyone say they received any money. Its all a scam. And if you want the junk mail to stop, start there. I think they do mostly internet now but if they still mail and its a self-addressed envelope put as much paperwork sent in that envelope with your address as they open the envelope. On the address put...take me off ur mailing list and any other name assoc with this address. Go on-line on their site and do the same thing by email. They sell your address. I have hardly any junk mail since I receive nothing from them. I stopped doing the Win a car/vacation thing at the mall. No junk mail.

Do what I said with junk mail you get. I got Mom down to almost nothing. I get the car coverage renewal thing and some local ads. Now Medicare stuff because of open enrollment. All just go in the trash. I no longer get any charities. And if I do, I email them to stop. If legit, they must comply.

When looking back the first sign of Dementia with my Mom was not being able to reason with her. I have a nephew with multiple disabilities move in with her at 18. He has a neurological problem that effects his maturity. She believed him over me. I could not understand why she was so unreasonable. Now I know. No matter what is said to him, he is not going to process or remember what you have said. So you now have to take the check book and credit card away. If he paid by credit card, the CC maybe able to stop the the payment or take it back. Your husband is now incompetent to handle his finances. Mute your phone so it doesn't ring if a landline. Or disable it if u have a cell phone you can use. If he has a cell, lose it. I know these are the last things you want to do but you have to protect what money you have.

My mom died with 4 bins completely packed with PCH sweepstakes envelopes and inserts. She saved them for over 40 years, believing that she was always going to win and she'd ALWAYS buy some little junky something to 'increase her chances' of winning.

When you cannot walk around your kitchen b/c there are so many boxes of old catalogs and these tons of sweepstakes envelopes--you're NOT winning.

Luckily, she couldn't use her cell phone or she would have given away every cent she had to scammers on the phone.

Towards the end of her life, we simply brought the mail in and tossed all pleas for money or catalogs out before she got her mail brought in to her.

All I have is run don't give in. Remember our information is all over the internet and our age. If this is true verify this. If he did the lottery here they wouldn't have contacted him, you are the one who matches your number to the winning number.
If this is out of the country don't listen to them. Find out if there is a way to verify this without the people who are calling you. Most likely this is a scam. Block the number.

He does not need to be driving. Dementia is not a disease one can turn on/off. As in being duped by scammers but then being perfectly fine to drive.

This, unfortunately, is something that many of us have dealt with. There have been a lot of suggestions, and rather than repeat them, it might be quicker to just locate the previous posts. Click on the tailed circle to the left of your avatar on the blue to green bar at the top of the page, search for "scam artists", "scams", and then choose which threads might be the most appropriate.

What others might suggest, and I wouldn't disagree, is determining how to take control of his finances so that he's either limited to a nominal amount of spending (for legitimate things, which the family could help with by taking him shopping), or more aggressive action, but that might require him executing authoritative documents giving the family more control, and that might not be amenable with him.