At 53 is is very important to maintain your muscle, at 60lb over you still have plenty of leeway so 1.5 lb per week is fine, however do not eat back calories from lifting, the calorie burn is really not very much unless you are doing very heavy large compound movements. All strength training is beneficial, it is not the small weights that shrink your muscles, it is the calorie deficit. When you loose weight some of it will be fat, some of it will be muscle, the ratio depends on several factors, including the size of calorie deficit, how much fat you have to loose, and the type and style of exercise you are doing. Weight training changes the ratio in favour of keeping muscle but Lifting heavier for fewer reps is better than adding a whole lot of lighter reps when in calorie deficit. Bodybuilders looking to build size will often use lighter weights for moderate reps to build size but this is only when they are in calorie surplus.
As for the 5lb weights, do you have difficulty carrying shopping bags ? if not then 5lb weights are way too light.
Yoga is great for your flexibility, but is also not a big calorie burner.