Congrats on your gains so far! That's excellent.
Aside from Liposuction, there is no such thing as spot reduction when it comes to weight loss. Where you hold fat is mainly genetic. At 70 years old, your skin has lost a lot of its collagen so it'll take longer to unstretch itself. Or it may never go away. The best things you can do are to add more muscle mass to increase your metabolic rate and stay very very hydrated. Also, include foods into your diet that can help boost your collagen.
Situps and other core exercises will help build support muscles that can prevent injuries later in life. They will not necessarily make the flab go away, but there a ton of other ancillary benefits.
These are lessons I learned while going from 298lbs to 190lbs. It was extremely difficult. Lots of sacrifice and sweat. I probably added 10 years to my life and thwarted Type 2 Diabetes. My Father has T2D, so that was my main motivation to lose the weight. I hate needles!
Good luck
