I can appreciate them wanting to find the cause instead of just treating the symptoms but I also understand how it feels when you’re the patient. It sucks being patient and waiting and getting no answers or help. Hopefully it pans out soon.
In the meantime, you know your body best. Use good judgment and do what you can but back off when your body tells you to do so.
I think a maintenance type program would be best. Just try to maintain what you have left in terms of muscle and strength. I’d start out by going to the gym and just doing what feels good. You don’t need a plan or progression at this point; you just need your gym therapy sessions and some muscle simulation.