Mitch's mother seems to be in good mental health, despite previous and subsequent episodes in which it is stated she has Alzheimer's.
When Sara gives Mitch his lunch, the rolled-up part of the bag faces toward him. In frontal shots of Mitch, the rolled-up part faces her.
A tether can be seen tied to Sara's boat as she and Mitch jump from it, indicating she was not as isolated as we were led to believe.
In some long shots of Sara's burning boat a tether is visible, indicating she is not as isolated as we are led to believe. Also, the fire somehow diminishes itself when Mitch comes to the rescue.
When Sarah is in Mitch's office, he fills a mug with what's clearly coffee and gives it to her. Just before he leaves, he says, "...finish your tea, okay?"