Hello there, since you would like some thoughts on your idea I'd share mine.
First off it really doesn't make sense why 'Jack' would have this 'psychotic' devotion/ secret fanatical love of Moreau after meeting him in highschool. its once thing to have your character have this secret crush on Moreau, but since Moreau is reclusive and stays out of the public light for the most part, and wouldn't be reachable, I doubt someone could keep up this mostly imagined love/devotion of moreau for so many years. people go to college, they get jobs, they have things to do, wash the dishes, take out the trash, stuff like a high school crush would get lost in the drudgery of everyday life.
And the idea of Jack being left a 'multimillion' business once his parents die is a bit tacky and unrealistic, most buisinesses when they get to be that big are 'owned' by many people, the CEO, board of directors, people possessing stock in the company, ect ect. If Jack's parents did die, all that Jack would really inherit would be a bunch of stock in the company and maybe his parent's pension or something like that.
Also there is someone already on the island that Moreau is being made to be Moreau's loyal dog, so you might want to keep that in mind.
Now that the unpleasent part of telling you what is wrong with your idea, how about I tell you how you can improve this.
Alright, Dr.Moreau has a list of people he knows that have wronged him or he just doesn't like and wants to get even with. If you still want Jack to be gay, here is an angle to consider:
During Highschool Jack does have a bit of a crush on Moreau, but never got around to sharing feelings about that and did end up sending the 'secret' love letters to Moreau, maybe going as far as starting to stalk Moreau. But somehow Moreau and his family finds out who it is, and Jack has to transfer to another school because of the threat of a restraining order.
Now you can put down what you wish for occupation, but I would seriously reconsider the 'multimillion' business owner, from what I guess about Jack it would be more probable that he might be the manager to some pizza shop.
And how does Jack get to the island? well if Jack is on that list of moreau's for embarrousing him with those letters and people in HS thinking moreau might be gay, then it probably be easiest to have your character jack win a vacation, unknowing what Moreau plans to do to Jack until Moreau gives Jack the needle