Can muscle wasting make you significantly weaker? i'm finding my physical job much harder after weight loss due to poor nutrition went fr 167 to 150

Absolutely: If you don not take in enough protein then your body breaks down muscle to meet it's needs. Less muscle = less ability for strenuous work.

Glycogen Depletion: Your weight loss may have been mostly due to glycogen depletion. Glycogen is a water- gel of starch-like material stored in your muscles. If you exercise more than usual, or go on a low-carb diet, this stored form of carbs gets used up. You lost weight mostly because the water in the starchy gel got peed out after the carbs were burned. Permanent weight loss requires you to use stored fat.

Energy deficit: You need to make sure that you are giving your muscles enough fuel. At your weight and doing physical work you should be eating around 200 grams of carbohydrates per day for energy. Then you also need about 80-90 grams of high quality protein and as much healthy fat (like olive and coconut oil) as your body wants.

Sure: Smaller muscles are weaker muscles. But why are you experiencing muscle wasting in the first place? Hand numbness could have something to do with this. See your regular doctor of perhaps a neurologist for a full assessment.