I don't know about any of this the way that you do, but lets walk through it.
What about the permanent pacemaker and cardioverter-defibrillator implantation? Can you ask about it?
How aware is Jared of what is happening to him? How miserable is he? Not what you see, but what he feels.
If you were to lower the medication and let him suffer there could be a treatment in 10 to 20 years that would greatly improve his mental state. I know I suffered greatly for 20 years. Would that be something he could live with?
What does Jared want? Is he old enough to understand? Have the risks been explained to him? Does the risk of death outweigh the suffering from living without the medication? If you knew that there would be treatment in the future would you take the same risk?
There is no easy way out of this for now. Not for you and not for him. It's an extremely hard place to be in.
Clozaril and a pace maker seems like the best solution if the beta blockers don't work. Maybe you could back off the Clozaril until you explore these options.
You are doing everything you can and you're faced with really hard choices. I know you must also feel like you're trapped with no way out. That's a scary place to be and it can cause some major depression. I think a therapist would really be good for you while you go through this. It's too hard to do this alone.
We're all here for you.
Hugs,
MG