Just being honest, I am surprised that the other doctors haven't really explored why you want this procedure given that you are over 50 and have had it since teenage and why at 300 pounds you think this will help your happiness with your body. Doing it now just sets you up for further body image unhappiness.
The problem is that older patients and especially excessively thin or excessively overweight patients do not get great results and the tubular deformity is about the toughest starting point for a decent breast augmentation and lift. Notice also how widely separated your breasts are as this makes getting cleavage extremely difficult.
So, what I am saying is that it will be very hard to give you a great result, certainly not possible at 300 pounds. So, if you want to do this and love your body better, the best thing is to first lose the weight and then do the surgery. If you have watched TV's Biggest Loser, you have sen that this can be done with diet and exercise coaching in a matter of months, not years. Good luck!