Bodyfat--Perplexed

I am 51 YO and have recently lost 87 lbs. At 5’8" and 153 I don’t want to lose more weight. Granted, I started at 42% BF, in November 27.7%, yesterday 21.3%. So there is progress. I workout 5x a week, 2 days on, 1 off, an hour each time, mostly Ian King routines. Each week my numbers look better, weights and reps. My diet is 30% fat, 55% protein, 15% carbs and I’m just above ketosis with good energy. I am taking in about 1700-2000 kcal/day–I still have a low metabolism and that seems to work fine. What bothers me is I am actually skinny now, and I don’t look fat, but I think 21.3% is way too high. Without losing more weight, what suggestions do you have for increasing my LBM? I’d like to get to 12% which is a stretch for my age but I think doable.Thanks!