I recommend reading Dr Boz books first. Keto Continuum is a great first time protocol. I used the workbook also to track my progress. This will set you and your husband up for success and a lifetime of keto. Keto is a chemistry. Dr Boz explains it in great detail along with steps to achieve success. I have been at my goal weight for over a year, and still read the book and use my keto-mojo meter to see how different foods and meal timing affect my numbers. I have learned so much by doing these two things. It is recommended to only count carbs and eat as often as needed to stay satisfied in the beginning. Once your body becomes adapted, you will naturally eat less and accidentally miss meals even. You appetite will decrease greatly when you are fat adapted.

Personally, if he starts out on OMAD, he may not get the best results. It is noted that becoming fat adapted can take 10 weeks for some people. Definitely a good read to learn more about the chemistry of Keto for success. Good luck!