GREAT JOB!!
There's nothing better than having a happy doctor!!
The BMI chart is definitely not the end all be all of healthy weight. There are a TON of factors it doesn't consider. Age and frame size are just two important factors that aren't considered. Listen to your doctor and listen to your body. Like you said, get down to 150 and see how you feel...
And again...FANTASTIC JOB!! Keep up with the great work!!