I find it odd he emailed you at work if you hadn't given him your email there. I would expect him to try calling you at work before emailing. I think it would be good to talk with him about how you wish to be reached in situations like this.

My T has canceled several times in the last few months, the night before the appointment. That is frequent for him. In prior years it was less. He is able to minimize the cancellations by scheduling only one appointment at a time. That way his schedule is more or less "set" by the time I and other clients make our appointments, so the chance of cancellation is less.

Does your boss know you are seeing her husband for therapy? I would worry that it would be hard for you to discuss work matters with him if his wife was part of the subject of discussion due to her being your boss. Could be kind of sticky!