I am a grown adult who was a micro preemie at birth, weighing 1lb, 9oz. Could I still have impaired lungs and impaired lung function from BPD?

Possible. It is possible but you would still be having problems if you did. If you have been doing well, any residual damage is minor.
Hard to tell. If you have no symptoms and no difficulty breathing and no difficulty when you exercise then the chances are any damage done was negligible and inconsequential.