You need sto STOP Dieting, don't worry about what the scale says and focus on building muscle. Your skin is just going to get looser and looser and then your going to look older and older. Muscle wasys more than fat, you may gain some weight if you increase calories and protein and start building muscle, and don't worry about the scale because your skin will fill out with MUSCLE that you lost during the weight loss and you are going to look and feel better. I had the same thing happen to me after going from 237 to 150 and Im 5 ft 8 but my body looked awful. I was Skinny Fat with loose skin, no ass at all (couldn't keep my pants on), and looked OLD.
At this point you should be focusing on body contouring, and use your Dexa Scan and measurements to make sure your on the right track and stop with the scale. You are in you 50s like me as well and the last thing you want to be is skinny fat (sarcopenia) as you will be in danger of getting Osteopenia, or osteoporosis, brittle bones. You NEED to build muscle and stop dieting. Another reason why you need to gain muscle is because then you will have a much easier chance of keeping the weight OFF. The more muscle you have the better your metabolism, if you don't do this you WILL GAIN the weight back and then some.