Hello and welcome to the group! It takes a long time to fully heal after a Thymectomy. When I had mine there was a man in the next ICU room who against his doctor's orders, lifted something heavy and snapped a wire in his chest. He had to have another surgery to have it repaired. So, my 'tip' to you would be listen to your doctor.
Sounds like you are recovering nicely and already see improvements...good to hear. Be patient and you'll be back to your normal routine in no time. Take care and let us know how you're doing.
Hugs,
Pat