Considering his age and behavior, I would get him an appointment with the vet as soon as the vet is comfortable doing the procedure. Make the appointment now for whenever that is. (An experienced vet may decide he’s ready.)
It is definitely hormones. Keep your son from “invading his habitat” as a child is seen more like a large animal and is more threatening. Let him sit by the xpen and have Frappe approach for pets. Be ready to pull back from nipping. He will be this way for one month after the surgery, but then he will calm down.
Is there a room he can run in for a while each day? Can you take him into a bathroom or bunny-proofed den for some play and exercise time? (Or just a hallway he can run up and down with doors to rooms closed?) Also, give him some toys he can tear up, like a willow ball or a phone book to shred. Hang in there, because it IS hormones and it will be over before you know it. Just get that appointment! 