Next time the carers / MIL phones, you take a deep breath and a say you can't get there until the weekend. If they phone at the weekend, you can't get there until Wednesday. The others are so right - if one of you goes over every time they call - they will keep calling. And the appropriate level of care package will not be offered to your MIL.
The thought of an elderly lady bed bound, doubly incontinent, not eating and drinking, living by herself with carers calling in 4 times a day (the standard maximum if you see what I mean) is ludicrous and cruel.MIL.
You sit DH down and spell out the implications for your family life if he's dashing off to his Mum's every day - 40 mins there, 40 mins back, an hour or so there - that's every evening gone. His work may be sympathetic for while, but that will not last, look at a max of a week or 2. So does he plan to resign and if so what will he do about paying bills, etc. If your MIL is doubly incontinent, falling out of bed, not eating or drinking she won't just need one carer there 24/7, she'll need 2. So he'll be there and he'll still need another carer to help lift / turn / change etc. If this is a step he wants to take, your family need to walk into that decision with your eyes wide open. And be under no illusion it will not be an easy road with such a frail patient.
You need to watch the concept of capacity; while it's a worthy concept, it is fundamentally flawed in the way it is followed by SS etc. They all take the view that if someone can express an opinion, then that opinion must be adhered to. Irrespective of whether it is diametrically opposite what anyone else in the family wants or needs, even if it's patently obviously unsafe, irrespective of whether the patient is confused, demented or just plain stubborn. Basically the support at home has to fail and fail big time, before SS will call time and agree that the situation is unsafe and over-ride the care needer's preferences.
Start asking around locally for the names of recommended care homes near you ( or at least the ones to avoid).
You have my sympathy - your and your DH are in for a rough, tough ride