I'm not sure that it's a badly contrived plot. Tybalt is an unpleasant person and he definitely wants to keep the mc away from Jill. He saw this as an opportunity to drive the wedge.
When Jill asks where the fire was he tells her that he doesn't want to worry her about those details (obviously we know the truth).
When he tells Jill to stay away from the MC, we don't see that actual part of the conversation, but it's unlikely that he said, "unless you stay away from mc and suck my cock, I'm pressing charges!". He would have gone with the whole, "this mc is a really bad influence, I'm very worried about you hanging out with him, just look what he did to the mansion, if you're not going to stay away from him for your own good, I will be forced to have him charged, you know I only have your well being in mind, and by the way, my cock is very lonely. Now are you sure you don't want to partake in this watermelon?".
Whether it would stand up in court or not is not the point, it's whether it would convince Jill to back off.
To be honest, if I was Tybalt and the MC did this to me, I'd be looking at how to hit him hard, I'd look at suing for damages (I imagine there'd but a lot of electrical equipment that took a hit once the sprinklers came on).