Thoughts on my outdoor enclosure?

I just moved my sulcata outdoors permanently. I’ve had him for 6 years and he has been raised inside because he was too small to be kept outside. I was waiting for his size to dictate a bigger enclosure, but it is just slow going. I had the proper lighting/food/humidity etc, but he just wasn’t growing as fast as expected. He’s always very happy, active and ate well. Anyways I’m hoping keeping him outside full time will allow him to thrive and grow and catch up to his expected growth. He doesn’t like hay but I have it always available along with weeds, grass and occasional store bought greens. From my understanding, a 6 year old should be able to be kept outside permanently. Until I can heat it, at what temp would you guys bring him in? Im in south Texas so high humidity and cooler weather is a concern for respiratory infections. I find myself very anxious about leaving him out 24/7. Any advice?

If that picture is the current size at six years old, your tortoise is not ready to live outside full time. They should be moved outside full time at around 8-10 inches. Prior to that, they can go outside during fair weather for a few hours a day. When they are moved outside full time, they need a heated insulated shelter that doesn't drop below 80 degrees. If the days are cool, then I bump the thermostat up to 86. December is not a good time to move one outside. This is not a species that does well with cold.

I don't introduce hay to them until they are around 12 inches.

There isn't a simple answer about temperatures for outside. There are too many variables. If its sunny, the pen is south or southwest facing, the ground is dry, its not windy, etc... Then 65 might be okay for a short while. But if they go park in a shady corner under such conditions, there is no point in them being outside. Ordinarily, I want it at least mid 70s and sunny before I see any point in putting a small sulcata outside.