It is clear that Elliot is a victim of Garst's abuse and grooming. He is also a teenager. He is cute because he is a child. Why would you want to flirt with a minor????
And no, I don't think there would be any jealousy, because both mc and Elliot are abused by him. Elliot even says how he was happy at first when we showed up, because he hoped Garst's aggression wouldn't be solely on him, and that it would be easier for him to manage.