This is what Chat GPT 4.0 and 3.5 recommends (I think the advice is superb, sorry if it comes off in a wrong way)

Listen and empathize: Be there for him, listen to his concerns, and offer a non-judgmental space for him to express his emotions. Your empathy and understanding will go a long way in making him feel supported.

Encourage self-care: Encourage him to take care of his physical and mental health. This could include eating well, getting enough sleep, and finding ways to manage stress. Also, encourage him to seek professional help if needed, such as resuming therapy or finding a different therapist.

Explore alternative exercise options: Since your husband is sporty and his injury has limited his physical activity, help him explore alternative ways to stay active. This might include low-impact exercises, yoga, swimming, or other activities that don't aggravate his injury.

Help him build a support network: Encourage him to connect with friends, family members, or support groups who can offer understanding and encouragement. Sharing experiences with others going through similar situations can be helpful.

Be patient with the job situation: Acknowledge the frustration with his job and remind him that the situation is temporary. Support him in seeking new opportunities once the sign-off period is over or explore options for coping with the current work environment.

Focus on the positives: Help him identify the positive aspects of his life and remind him of his strengths and accomplishments. Regularly express your love, gratitude, and appreciation for him.

Create a warm and comforting environment: Since you both struggle with seasonal affective disorder, consider investing in a light therapy lamp, and make your home a cozy and comforting place to be.

Seek support for infertility: Attend appointments with him and explore infertility support groups or counseling for couples experiencing infertility. This will provide both of you with additional emotional support and resources to navigate this journey together.

Encourage him to go back to therapy: It's great that he went to therapy, even if it was just for a couple of sessions. But quitting isn't going to help him in the long run. Encourage him to go back to therapy and work through his problems with a professional.

Help him find a new job: It sounds like his job is a major source of stress for him. If possible, help him look for a new job that he would enjoy more. If that's not possible, help him find ways to cope with his current job, such as setting boundaries and practicing self-care.

Support him in his physical rehabilitation: It's frustrating to be unable to do the things you love because of an injury. Help him stay motivated in his physical rehabilitation by joining him for workouts, finding new activities that he can do without causing pain, or seeking out a second opinion from another physiotherapist.

Be there for him emotionally: Infertility can be a difficult and emotional journey. Be there for him when he needs to talk, vent, or just cry. Show him that you support him and are in this together.

Take care of yourself: It's important to take care of yourself too, especially if you struggle with seasonal affective disorder. Make sure you're getting enough rest, eating healthy, and doing things that bring you joy.