Hi Swimtime,
So glad the shooting pains are gone! That is tremendous!
I know the PT has been a bit of a struggle for some time. It sounds like there are pros and cons. I believe the discipline of it is positive - measured repetitions, times, increased types of exercise. Also Ensuring optimal and close to normal range of motion, a common deficit with ankle injuries! Is important. However, if you are methodical you can achieve this yourself. Being wiped out for two whole days after doesn't sound so good. Is there anything they do or plan to do that you cannot? If you decide to drop it I would talk with PT first, make sure you aren't burning any bridges with your insurance on restarting later and make sure they send you home with an exercise plan to do on your own.
The bike is a available at the gym, bands can be cut to take home, you can buy a wobble board (I bought an Avenco) and have him do reps front to back and in a circle with the edge to the floor. When ready, He can start standing on just the injured foot to increase balance and ankle stability. Throwing a ball and bouncing it off a wall to yourself while doing this is helpful too. I personally think the treadmill should come last, it is a lot of heel to toe stress. It is easier to manage gait just walking in the neighborhood or on a track. Elliptical can add leg strength and won't stress things as much while still giving ankle motion. IF he tolerates it. Try new things one at a time for only a few minutes at a time, ie: no more than 5 max. That way if there's a flare you know what to pull back on and you limit how bad it is.
The water has many benefits (natural gradient compression) however at cool temperatures it is not always possible to feel something being overtaxed so while jumping or stretching may not feel bad at the time it is always good to be careful.
On elevation, ortho has told me bone repairs take 18 months for complete remodeling. Swelling and aching to some degree is normal during this time. Elevation is helpful. With CRPS the circulation damps down, gets overloaded and can't filter out enough fluid or inflammatory compounds. If elevation helps with this, especially after challenging it then go ahead. So long as he is keeping it down some of each hour so his autonomic system doesn't forget what to do about Gravity it should be okay.
If the kid is having fun at the Y and you can build in the discipline so you have measurable progress I see no harm in trying. Having his full investment in what he's doing will go a long way. On meds, has he tried nortriptyline? My neuro stated he gave it out "like water" for teens with migraine. I now only take 10mg, no goofiness factor at all at that dose and an edge off the pain.
Follow your instincts, you know your cub better than anyone. Sometimes they need someone else to teach them, tutor them, challenge them and sometimes they need the power of Mom.
Take care, I am sending more Healing Love,
Littlepaw