sue1169 I so sympathise with you, my FiL was like that, except that in his case it wasn't dementia. He was depressed and clumsy and his doctor knew there was a problem as well so had him coming to see him monthly, even though his only medical problem was high blood pressure. Every visit the doctor asked how he was feeling, 'Fine' he would say, then one day he collapsed in the street. Fortunately outside the surgery, which was also near his home. By the end of the day he had a diagnosis of Parkinson's disease.
The tragedy for you, sue, is you may have to wait until your DH goes for a walk gets lost and either collapses or you report him as missing, before anything can be done.
It is the 'Catch 22'. Neither the doctor, nor anybody else, can do anything about seeing him and assessing his mental condition until he chooses voluntarily to see the doctor and admit the problem. Officially until he admits he has a problem there is nothing wrong with him, so no-one can interfere - until the crisis strikes.
As you say, 'what a mess'. Would he listen if his children spoke to him instead of asking you to act? I know my DD can often get DH to respond well to awkward truths when I cannot.
Meanwhile stay with us, we can only offer sympathy and virtual
but many of us have had experiences like yours, or varieties there of, and understand only too well the struggle your life is at present.