He's wandering around outside in December while very ill. Does that sound like keeping him safe?
And yes, I've rung 111 plenty of times during my dad's two-year terminal illness, thank you, including when he was so confused he thought he was at an address where he hadn't lived for 60 years and when he thought I was poisoning him, among other things.
Since you clearly haven't dealt with this, as I can tell because you asked what they could do, I'll tell you: A nurse answers and they ask a bunch of questions. A LOT of questions. Depending on the nature of the illness, they either send an ambulance, go away and call a doctor and call you back with next steps, or tell you to get yourself or your loved one to A&E if that will be quicker than an ambulance. They let the facility know to expect you and what the problem is, so that they're ready for you when they arrive. If you can be seen at a walk-in clinic, they tell you which one to go to and they similarly inform the clinic.
They're pretty good when someone is seriously ill, like OP's husband.
I hope I've answered your three questions: The above is what they can do; yes, I have "rung 111 with this kind of issue;" and yes, I have "personally dealt with" something like this. Dad died a few months ago and mental confusion was part of his illness at both the end and in the summer of 2023. Happy now?