!. You're doing it right. The heating, UVB and light needs to be pushed to one side, so that he can move to a dim, cooler side of the habitat, as his body dictates.
2. In the wild, the forest floor and the lower shaded parts of the tree trunks are used often by igs to regulate their body temperature. You are creating a heat gradient as it should be, from the right to the left and from the top to the bottom.
3. Hide boxes can help stressed and even tame iguanas. Some like them, dome don't use them. IMO it's a necessary furnishing for the floor of the cage. I made min to mimic a deep crack in rock. Just two pieced of wood joined at right angles Make a v-shaped hide. It should be snug from side to side, and just enough room above so he can crawl in without dragging it. I made mine with 1/8 inch plywood and weighed it down with hot-glued-on rocks or lead. They need to be as long as the total STL (Snout to tip of tail) of your ig.
4. Wherever you put it he will find it. Keep in mind that habit changes can plunge igs into a short season of stress (relocation stress), during which he won't eat. I bet that within three days he will know the entire setup. If you put a kitty litter sized box with 2 inches of water, he will defecate in it. For his water he needs something he can't climb into. A 6 inch diameter dish with 1 1/2 inch tall sides will work for an ig the size of yours.
5: Humidity. He must have as close as you can get to 80% relative humidity. Organ failure, especially the kidneys, happens over a period of years without enough water intake. The result is common: early death. His natural life span is over 25 years but few igs make it even to 15 years. IMO, chronic dehydration is the culprit. You may need three cool-mist humidifiers to approach that. Your heating may need to be increased to handle the extra load of droplet evaporation.
Look up http://www.anapsid.org/pdf/icfs.pdf That has everything you need to know. I hope it works. I'm in the boonies using dial-up, so I can't test it. It won't load for me.
Hope this makes sense,