Dave,

You are asking alot! Your weight loss is really good. I am new here too, but was on lc several years ago. Are you taking supplements? vitamins, chromium? Omega 6 oils?
Are you drinking enough pure water?

It doesn't matter if you don't make the Dr.s request. One day at a time. Let the Dr. know you were off in your weight estimate, and how you have been doing.
As far as exercise, I am not the one to answer that question, but off the top of my head, some small weight training would probably good, as well as water exercise, to take the strain off your legs.
Make sure you eat enough! Try posting your foods daily-start a journal to track your progress. That way if you run into trouble, others can help. God Bless, Tina