Hi Fairy and welcome to TP
I understand what you're saying my wife was diagnosed in her mid 50's and I had to give up work a year or two later things got worse, I lost her in IKEA one time and needed security to find her, she escaped from the house while I was putting the washing out and I found her a few hundred yards away dressed in her nightie and clutching her usual stuff (2 hair brushes and a few ornaments).
Sleeping I had a gate at the top of the stairs but fixed to take an adult weight and not one she might climb over and fall down stairs or get out, certainly I hid all the keys but I never left her in the house alone.
Sixty two is young for your husband but that age my wife had become so violent she was put in the cage in the back of a police van (the paramedics wouldn't go near) and sectioned and unlike your husband she was at that time 100% mobile.
Alarms, relying on neighbours and all the rest are a sticking plaster solution, they might work for now but how long is now, a week, a month or a year, eventually then will become now and you'll have to look to the future.
One problem is that as a younger person GP's and social services see you as capable, people suggest Attendance Allowance as they fail to read the bit that he's under 65, I always thought the last 10 years of our working lives (after the kids left home) would be a chance to build up a financial buffer but it wasn't, from earning a good wage I went onto £62pw carers allowance and stuffed my/our chance of a good retirement.
Early onset dementia comes with a list of problems that the post retirement people don't necessarily appreciate, not the least of which is losing that last, valuable 10 years of your working life and all the benefits that brings not the least of which is earning and saving and not eating through your savings and getting £63 quid a week for a 24 hours 7 day a week job.
K