I'm so sorry to hear that! I know it's terrifying to lose so much so quickly.
I assume you already had/have had IV antibiotics and either are still on them or have stopped them for now?
Extra treatments - not sure how many times a day you're already doing airway clearance, but add 1 session.
Steroids are sometimes worth a try, though they usually don't help me much.
Exercise - start slow when coming back from such a big illness, but I like things that have impact like walking, running, jumping rope. Swimming is good too since you have to hold your breath. Some strength training of the core/upper body can also be really helpful both to rebuild strength you lost and to induce coughing.