Need Help with my Savvanah Monitor

I have been told different things by different people and its very frusturating. I handle him for at least 30 min a day, every day. I feed him superworms/mealworms with an occasional rodent. I am in the process of building him a wooden enclosure. He is in his hide spot all of the time and i have had him for 3 months. He hisses sometimes when i am handling him and he gets scared but always calms down. I need help with idea on what to do for his enclosure i am making it 8ft long, 4 ft wide, and 4 ft tall. but i want to know what i should install for his light fixtures, substrate etc. ANY HELP will be much appreciated thank you!