[anonymously]

Do not free feed. Feed twice a day. Pick up anything not eaten within 10 minutes, store in the fridg and offer at the next mealtime.
The guidelines on the dog food packages regarding amounts are usually too much. Add a splash of water to the kibble, especially if your dog isn’t a water drinker.

I might try a limited ingredient food, such as Nutrisca, check chewy.com for reviews.

Are you sure you are not feeding him too much?