Well, it is really good that you have a husband who listens and is helping you to form an action plan. He must feel worried about you.
Have you sat down with your manager one-to-one and had that conversation about the situation? Is your manager in the office?
If you want to keep the job, I have a suggestion. Dry your tears, and jump into action! Ok your next train journey get your laptop out and make a table. On the left hand column, make a list of your job responsibilities once the two new staff are working on the deliveries. In the next column, approx how much time per week spent on each of those tasks. In the next column note down whether those tasks must be done on a specific day of the week or time. In the last column wrote down whether you can do the tasks from home.
Then create a diary appointment for a sit-down with your manager, attach your list as pre-read, and ask him to discuss with you. When you have the meeting don’t speak too much, don’t go on about how hard you are finding it personally and the exhaustion of the commute. Just ask the question exactly as you have on your thread, “I don’t understand why my job requires me to be in the office when my job can be done working from home same as everyone else.”
In fairness most places of work do want someone to manage the workplace, just to ensure everything is running smoothly, have an on-site first aider etc.
It is definitely worth telling your manager that the situation you find yourself in is not possible to sustain and regrettably without the wfh adjustments you will be obliged to find a new job.