Simba really is georgous, I'm not surprised you are so very fond of him.

Like you, I have seen this lack of interest in food in a cat that is under stress several times and it's always scary. NewCat, who is sitting on my lap right now, was obviously underweight when I adopted her from the shelter, and all the time she was in her week's isolation (in a sunny bedroom) she ate just enough dry food to make a slight indentation in the mound. Wet food did tempt her a little more, but it wasn't until a couple of days after I let her out into the main area that she suddenly started to eat, and then ate really well. The relief was intense because I realized that she must have been eating tiny amounts in the shelter also to be so underweight. She had come from a stressful situation, she's Siamese, the shelter is crowded, she could have ended up at least making herself ill, it's an awful thought. But the quiet of a stable new home and new places to explore allowed her to recover her appetite.

I feel sure the same will happen with Simba. He is eating something and, best of all, he is showing an interest in his surroundings. While he may need more isolation so you can check how much he eats, his explorations and contact with you will surely give him the security and zest for life that will result in his suddenly starting to eat normally. Then you will have him under your feet in the kitchen demanding you open cans of wet food, as I do NewCat.

Your real problem is going to come later, as you look for a new home for him. His behavior will probably be repeated since it's already happened twice. Does this mean you just have to keep him?